--- a/env/lib/python3.7/site-packages/distlib/locators.py	Thu May 14 16:47:39 2020 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,1302 +0,0 @@
-# -*- coding: utf-8 -*-
-#
-# Copyright (C) 2012-2015 Vinay Sajip.
-# Licensed to the Python Software Foundation under a contributor agreement.
-# See LICENSE.txt and CONTRIBUTORS.txt.
-#
-
-import gzip
-from io import BytesIO
-import json
-import logging
-import os
-import posixpath
-import re
-try:
-    import threading
-except ImportError:  # pragma: no cover
-    import dummy_threading as threading
-import zlib
-
-from . import DistlibException
-from .compat import (urljoin, urlparse, urlunparse, url2pathname, pathname2url,
-                     queue, quote, unescape, string_types, build_opener,
-                     HTTPRedirectHandler as BaseRedirectHandler, text_type,
-                     Request, HTTPError, URLError)
-from .database import Distribution, DistributionPath, make_dist
-from .metadata import Metadata, MetadataInvalidError
-from .util import (cached_property, parse_credentials, ensure_slash,
-                   split_filename, get_project_data, parse_requirement,
-                   parse_name_and_version, ServerProxy, normalize_name)
-from .version import get_scheme, UnsupportedVersionError
-from .wheel import Wheel, is_compatible
-
-logger = logging.getLogger(__name__)
-
-HASHER_HASH = re.compile(r'^(\w+)=([a-f0-9]+)')
-CHARSET = re.compile(r';\s*charset\s*=\s*(.*)\s*$', re.I)
-HTML_CONTENT_TYPE = re.compile('text/html|application/x(ht)?ml')
-DEFAULT_INDEX = 'https://pypi.org/pypi'
-
-def get_all_distribution_names(url=None):
-    """
-    Return all distribution names known by an index.
-    :param url: The URL of the index.
-    :return: A list of all known distribution names.
-    """
-    if url is None:
-        url = DEFAULT_INDEX
-    client = ServerProxy(url, timeout=3.0)
-    try:
-        return client.list_packages()
-    finally:
-        client('close')()
-
-class RedirectHandler(BaseRedirectHandler):
-    """
-    A class to work around a bug in some Python 3.2.x releases.
-    """
-    # There's a bug in the base version for some 3.2.x
-    # (e.g. 3.2.2 on Ubuntu Oneiric). If a Location header
-    # returns e.g. /abc, it bails because it says the scheme ''
-    # is bogus, when actually it should use the request's
-    # URL for the scheme. See Python issue #13696.
-    def http_error_302(self, req, fp, code, msg, headers):
-        # Some servers (incorrectly) return multiple Location headers
-        # (so probably same goes for URI).  Use first header.
-        newurl = None
-        for key in ('location', 'uri'):
-            if key in headers:
-                newurl = headers[key]
-                break
-        if newurl is None:  # pragma: no cover
-            return
-        urlparts = urlparse(newurl)
-        if urlparts.scheme == '':
-            newurl = urljoin(req.get_full_url(), newurl)
-            if hasattr(headers, 'replace_header'):
-                headers.replace_header(key, newurl)
-            else:
-                headers[key] = newurl
-        return BaseRedirectHandler.http_error_302(self, req, fp, code, msg,
-                                                  headers)
-
-    http_error_301 = http_error_303 = http_error_307 = http_error_302
-
-class Locator(object):
-    """
-    A base class for locators - things that locate distributions.
-    """
-    source_extensions = ('.tar.gz', '.tar.bz2', '.tar', '.zip', '.tgz', '.tbz')
-    binary_extensions = ('.egg', '.exe', '.whl')
-    excluded_extensions = ('.pdf',)
-
-    # A list of tags indicating which wheels you want to match. The default
-    # value of None matches against the tags compatible with the running
-    # Python. If you want to match other values, set wheel_tags on a locator
-    # instance to a list of tuples (pyver, abi, arch) which you want to match.
-    wheel_tags = None
-
-    downloadable_extensions = source_extensions + ('.whl',)
-
-    def __init__(self, scheme='default'):
-        """
-        Initialise an instance.
-        :param scheme: Because locators look for most recent versions, they
-                       need to know the version scheme to use. This specifies
-                       the current PEP-recommended scheme - use ``'legacy'``
-                       if you need to support existing distributions on PyPI.
-        """
-        self._cache = {}
-        self.scheme = scheme
-        # Because of bugs in some of the handlers on some of the platforms,
-        # we use our own opener rather than just using urlopen.
-        self.opener = build_opener(RedirectHandler())
-        # If get_project() is called from locate(), the matcher instance
-        # is set from the requirement passed to locate(). See issue #18 for
-        # why this can be useful to know.
-        self.matcher = None
-        self.errors = queue.Queue()
-
-    def get_errors(self):
-        """
-        Return any errors which have occurred.
-        """
-        result = []
-        while not self.errors.empty():  # pragma: no cover
-            try:
-                e = self.errors.get(False)
-                result.append(e)
-            except self.errors.Empty:
-                continue
-            self.errors.task_done()
-        return result
-
-    def clear_errors(self):
-        """
-        Clear any errors which may have been logged.
-        """
-        # Just get the errors and throw them away
-        self.get_errors()
-
-    def clear_cache(self):
-        self._cache.clear()
-
-    def _get_scheme(self):
-        return self._scheme
-
-    def _set_scheme(self, value):
-        self._scheme = value
-
-    scheme = property(_get_scheme, _set_scheme)
-
-    def _get_project(self, name):
-        """
-        For a given project, get a dictionary mapping available versions to Distribution
-        instances.
-
-        This should be implemented in subclasses.
-
-        If called from a locate() request, self.matcher will be set to a
-        matcher for the requirement to satisfy, otherwise it will be None.
-        """
-        raise NotImplementedError('Please implement in the subclass')
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        raise NotImplementedError('Please implement in the subclass')
-
-    def get_project(self, name):
-        """
-        For a given project, get a dictionary mapping available versions to Distribution
-        instances.
-
-        This calls _get_project to do all the work, and just implements a caching layer on top.
-        """
-        if self._cache is None:  # pragma: no cover
-            result = self._get_project(name)
-        elif name in self._cache:
-            result = self._cache[name]
-        else:
-            self.clear_errors()
-            result = self._get_project(name)
-            self._cache[name] = result
-        return result
-
-    def score_url(self, url):
-        """
-        Give an url a score which can be used to choose preferred URLs
-        for a given project release.
-        """
-        t = urlparse(url)
-        basename = posixpath.basename(t.path)
-        compatible = True
-        is_wheel = basename.endswith('.whl')
-        is_downloadable = basename.endswith(self.downloadable_extensions)
-        if is_wheel:
-            compatible = is_compatible(Wheel(basename), self.wheel_tags)
-        return (t.scheme == 'https', 'pypi.org' in t.netloc,
-                is_downloadable, is_wheel, compatible, basename)
-
-    def prefer_url(self, url1, url2):
-        """
-        Choose one of two URLs where both are candidates for distribution
-        archives for the same version of a distribution (for example,
-        .tar.gz vs. zip).
-
-        The current implementation favours https:// URLs over http://, archives
-        from PyPI over those from other locations, wheel compatibility (if a
-        wheel) and then the archive name.
-        """
-        result = url2
-        if url1:
-            s1 = self.score_url(url1)
-            s2 = self.score_url(url2)
-            if s1 > s2:
-                result = url1
-            if result != url2:
-                logger.debug('Not replacing %r with %r', url1, url2)
-            else:
-                logger.debug('Replacing %r with %r', url1, url2)
-        return result
-
-    def split_filename(self, filename, project_name):
-        """
-        Attempt to split a filename in project name, version and Python version.
-        """
-        return split_filename(filename, project_name)
-
-    def convert_url_to_download_info(self, url, project_name):
-        """
-        See if a URL is a candidate for a download URL for a project (the URL
-        has typically been scraped from an HTML page).
-
-        If it is, a dictionary is returned with keys "name", "version",
-        "filename" and "url"; otherwise, None is returned.
-        """
-        def same_project(name1, name2):
-            return normalize_name(name1) == normalize_name(name2)
-
-        result = None
-        scheme, netloc, path, params, query, frag = urlparse(url)
-        if frag.lower().startswith('egg='):  # pragma: no cover
-            logger.debug('%s: version hint in fragment: %r',
-                         project_name, frag)
-        m = HASHER_HASH.match(frag)
-        if m:
-            algo, digest = m.groups()
-        else:
-            algo, digest = None, None
-        origpath = path
-        if path and path[-1] == '/':  # pragma: no cover
-            path = path[:-1]
-        if path.endswith('.whl'):
-            try:
-                wheel = Wheel(path)
-                if not is_compatible(wheel, self.wheel_tags):
-                    logger.debug('Wheel not compatible: %s', path)
-                else:
-                    if project_name is None:
-                        include = True
-                    else:
-                        include = same_project(wheel.name, project_name)
-                    if include:
-                        result = {
-                            'name': wheel.name,
-                            'version': wheel.version,
-                            'filename': wheel.filename,
-                            'url': urlunparse((scheme, netloc, origpath,
-                                               params, query, '')),
-                            'python-version': ', '.join(
-                                ['.'.join(list(v[2:])) for v in wheel.pyver]),
-                        }
-            except Exception as e:  # pragma: no cover
-                logger.warning('invalid path for wheel: %s', path)
-        elif not path.endswith(self.downloadable_extensions):  # pragma: no cover
-            logger.debug('Not downloadable: %s', path)
-        else:  # downloadable extension
-            path = filename = posixpath.basename(path)
-            for ext in self.downloadable_extensions:
-                if path.endswith(ext):
-                    path = path[:-len(ext)]
-                    t = self.split_filename(path, project_name)
-                    if not t:  # pragma: no cover
-                        logger.debug('No match for project/version: %s', path)
-                    else:
-                        name, version, pyver = t
-                        if not project_name or same_project(project_name, name):
-                            result = {
-                                'name': name,
-                                'version': version,
-                                'filename': filename,
-                                'url': urlunparse((scheme, netloc, origpath,
-                                                   params, query, '')),
-                                #'packagetype': 'sdist',
-                            }
-                            if pyver:  # pragma: no cover
-                                result['python-version'] = pyver
-                    break
-        if result and algo:
-            result['%s_digest' % algo] = digest
-        return result
-
-    def _get_digest(self, info):
-        """
-        Get a digest from a dictionary by looking at a "digests" dictionary
-        or keys of the form 'algo_digest'.
-
-        Returns a 2-tuple (algo, digest) if found, else None. Currently
-        looks only for SHA256, then MD5.
-        """
-        result = None
-        if 'digests' in info:
-            digests = info['digests']
-            for algo in ('sha256', 'md5'):
-                if algo in digests:
-                    result = (algo, digests[algo])
-                    break
-        if not result:
-            for algo in ('sha256', 'md5'):
-                key = '%s_digest' % algo
-                if key in info:
-                    result = (algo, info[key])
-                    break
-        return result
-
-    def _update_version_data(self, result, info):
-        """
-        Update a result dictionary (the final result from _get_project) with a
-        dictionary for a specific version, which typically holds information
-        gleaned from a filename or URL for an archive for the distribution.
-        """
-        name = info.pop('name')
-        version = info.pop('version')
-        if version in result:
-            dist = result[version]
-            md = dist.metadata
-        else:
-            dist = make_dist(name, version, scheme=self.scheme)
-            md = dist.metadata
-        dist.digest = digest = self._get_digest(info)
-        url = info['url']
-        result['digests'][url] = digest
-        if md.source_url != info['url']:
-            md.source_url = self.prefer_url(md.source_url, url)
-            result['urls'].setdefault(version, set()).add(url)
-        dist.locator = self
-        result[version] = dist
-
-    def locate(self, requirement, prereleases=False):
-        """
-        Find the most recent distribution which matches the given
-        requirement.
-
-        :param requirement: A requirement of the form 'foo (1.0)' or perhaps
-                            'foo (>= 1.0, < 2.0, != 1.3)'
-        :param prereleases: If ``True``, allow pre-release versions
-                            to be located. Otherwise, pre-release versions
-                            are not returned.
-        :return: A :class:`Distribution` instance, or ``None`` if no such
-                 distribution could be located.
-        """
-        result = None
-        r = parse_requirement(requirement)
-        if r is None:  # pragma: no cover
-            raise DistlibException('Not a valid requirement: %r' % requirement)
-        scheme = get_scheme(self.scheme)
-        self.matcher = matcher = scheme.matcher(r.requirement)
-        logger.debug('matcher: %s (%s)', matcher, type(matcher).__name__)
-        versions = self.get_project(r.name)
-        if len(versions) > 2:   # urls and digests keys are present
-            # sometimes, versions are invalid
-            slist = []
-            vcls = matcher.version_class
-            for k in versions:
-                if k in ('urls', 'digests'):
-                    continue
-                try:
-                    if not matcher.match(k):
-                        logger.debug('%s did not match %r', matcher, k)
-                    else:
-                        if prereleases or not vcls(k).is_prerelease:
-                            slist.append(k)
-                        else:
-                            logger.debug('skipping pre-release '
-                                         'version %s of %s', k, matcher.name)
-                except Exception:  # pragma: no cover
-                    logger.warning('error matching %s with %r', matcher, k)
-                    pass # slist.append(k)
-            if len(slist) > 1:
-                slist = sorted(slist, key=scheme.key)
-            if slist:
-                logger.debug('sorted list: %s', slist)
-                version = slist[-1]
-                result = versions[version]
-        if result:
-            if r.extras:
-                result.extras = r.extras
-            result.download_urls = versions.get('urls', {}).get(version, set())
-            d = {}
-            sd = versions.get('digests', {})
-            for url in result.download_urls:
-                if url in sd:  # pragma: no cover
-                    d[url] = sd[url]
-            result.digests = d
-        self.matcher = None
-        return result
-
-
-class PyPIRPCLocator(Locator):
-    """
-    This locator uses XML-RPC to locate distributions. It therefore
-    cannot be used with simple mirrors (that only mirror file content).
-    """
-    def __init__(self, url, **kwargs):
-        """
-        Initialise an instance.
-
-        :param url: The URL to use for XML-RPC.
-        :param kwargs: Passed to the superclass constructor.
-        """
-        super(PyPIRPCLocator, self).__init__(**kwargs)
-        self.base_url = url
-        self.client = ServerProxy(url, timeout=3.0)
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        return set(self.client.list_packages())
-
-    def _get_project(self, name):
-        result = {'urls': {}, 'digests': {}}
-        versions = self.client.package_releases(name, True)
-        for v in versions:
-            urls = self.client.release_urls(name, v)
-            data = self.client.release_data(name, v)
-            metadata = Metadata(scheme=self.scheme)
-            metadata.name = data['name']
-            metadata.version = data['version']
-            metadata.license = data.get('license')
-            metadata.keywords = data.get('keywords', [])
-            metadata.summary = data.get('summary')
-            dist = Distribution(metadata)
-            if urls:
-                info = urls[0]
-                metadata.source_url = info['url']
-                dist.digest = self._get_digest(info)
-                dist.locator = self
-                result[v] = dist
-                for info in urls:
-                    url = info['url']
-                    digest = self._get_digest(info)
-                    result['urls'].setdefault(v, set()).add(url)
-                    result['digests'][url] = digest
-        return result
-
-class PyPIJSONLocator(Locator):
-    """
-    This locator uses PyPI's JSON interface. It's very limited in functionality
-    and probably not worth using.
-    """
-    def __init__(self, url, **kwargs):
-        super(PyPIJSONLocator, self).__init__(**kwargs)
-        self.base_url = ensure_slash(url)
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        raise NotImplementedError('Not available from this locator')
-
-    def _get_project(self, name):
-        result = {'urls': {}, 'digests': {}}
-        url = urljoin(self.base_url, '%s/json' % quote(name))
-        try:
-            resp = self.opener.open(url)
-            data = resp.read().decode() # for now
-            d = json.loads(data)
-            md = Metadata(scheme=self.scheme)
-            data = d['info']
-            md.name = data['name']
-            md.version = data['version']
-            md.license = data.get('license')
-            md.keywords = data.get('keywords', [])
-            md.summary = data.get('summary')
-            dist = Distribution(md)
-            dist.locator = self
-            urls = d['urls']
-            result[md.version] = dist
-            for info in d['urls']:
-                url = info['url']
-                dist.download_urls.add(url)
-                dist.digests[url] = self._get_digest(info)
-                result['urls'].setdefault(md.version, set()).add(url)
-                result['digests'][url] = self._get_digest(info)
-            # Now get other releases
-            for version, infos in d['releases'].items():
-                if version == md.version:
-                    continue    # already done
-                omd = Metadata(scheme=self.scheme)
-                omd.name = md.name
-                omd.version = version
-                odist = Distribution(omd)
-                odist.locator = self
-                result[version] = odist
-                for info in infos:
-                    url = info['url']
-                    odist.download_urls.add(url)
-                    odist.digests[url] = self._get_digest(info)
-                    result['urls'].setdefault(version, set()).add(url)
-                    result['digests'][url] = self._get_digest(info)
-#            for info in urls:
-#                md.source_url = info['url']
-#                dist.digest = self._get_digest(info)
-#                dist.locator = self
-#                for info in urls:
-#                    url = info['url']
-#                    result['urls'].setdefault(md.version, set()).add(url)
-#                    result['digests'][url] = self._get_digest(info)
-        except Exception as e:
-            self.errors.put(text_type(e))
-            logger.exception('JSON fetch failed: %s', e)
-        return result
-
-
-class Page(object):
-    """
-    This class represents a scraped HTML page.
-    """
-    # The following slightly hairy-looking regex just looks for the contents of
-    # an anchor link, which has an attribute "href" either immediately preceded
-    # or immediately followed by a "rel" attribute. The attribute values can be
-    # declared with double quotes, single quotes or no quotes - which leads to
-    # the length of the expression.
-    _href = re.compile("""
-(rel\\s*=\\s*(?:"(?P<rel1>[^"]*)"|'(?P<rel2>[^']*)'|(?P<rel3>[^>\\s\n]*))\\s+)?
-href\\s*=\\s*(?:"(?P<url1>[^"]*)"|'(?P<url2>[^']*)'|(?P<url3>[^>\\s\n]*))
-(\\s+rel\\s*=\\s*(?:"(?P<rel4>[^"]*)"|'(?P<rel5>[^']*)'|(?P<rel6>[^>\\s\n]*)))?
-""", re.I | re.S | re.X)
-    _base = re.compile(r"""<base\s+href\s*=\s*['"]?([^'">]+)""", re.I | re.S)
-
-    def __init__(self, data, url):
-        """
-        Initialise an instance with the Unicode page contents and the URL they
-        came from.
-        """
-        self.data = data
-        self.base_url = self.url = url
-        m = self._base.search(self.data)
-        if m:
-            self.base_url = m.group(1)
-
-    _clean_re = re.compile(r'[^a-z0-9$&+,/:;=?@.#%_\\|-]', re.I)
-
-    @cached_property
-    def links(self):
-        """
-        Return the URLs of all the links on a page together with information
-        about their "rel" attribute, for determining which ones to treat as
-        downloads and which ones to queue for further scraping.
-        """
-        def clean(url):
-            "Tidy up an URL."
-            scheme, netloc, path, params, query, frag = urlparse(url)
-            return urlunparse((scheme, netloc, quote(path),
-                               params, query, frag))
-
-        result = set()
-        for match in self._href.finditer(self.data):
-            d = match.groupdict('')
-            rel = (d['rel1'] or d['rel2'] or d['rel3'] or
-                   d['rel4'] or d['rel5'] or d['rel6'])
-            url = d['url1'] or d['url2'] or d['url3']
-            url = urljoin(self.base_url, url)
-            url = unescape(url)
-            url = self._clean_re.sub(lambda m: '%%%2x' % ord(m.group(0)), url)
-            result.add((url, rel))
-        # We sort the result, hoping to bring the most recent versions
-        # to the front
-        result = sorted(result, key=lambda t: t[0], reverse=True)
-        return result
-
-
-class SimpleScrapingLocator(Locator):
-    """
-    A locator which scrapes HTML pages to locate downloads for a distribution.
-    This runs multiple threads to do the I/O; performance is at least as good
-    as pip's PackageFinder, which works in an analogous fashion.
-    """
-
-    # These are used to deal with various Content-Encoding schemes.
-    decoders = {
-        'deflate': zlib.decompress,
-        'gzip': lambda b: gzip.GzipFile(fileobj=BytesIO(d)).read(),
-        'none': lambda b: b,
-    }
-
-    def __init__(self, url, timeout=None, num_workers=10, **kwargs):
-        """
-        Initialise an instance.
-        :param url: The root URL to use for scraping.
-        :param timeout: The timeout, in seconds, to be applied to requests.
-                        This defaults to ``None`` (no timeout specified).
-        :param num_workers: The number of worker threads you want to do I/O,
-                            This defaults to 10.
-        :param kwargs: Passed to the superclass.
-        """
-        super(SimpleScrapingLocator, self).__init__(**kwargs)
-        self.base_url = ensure_slash(url)
-        self.timeout = timeout
-        self._page_cache = {}
-        self._seen = set()
-        self._to_fetch = queue.Queue()
-        self._bad_hosts = set()
-        self.skip_externals = False
-        self.num_workers = num_workers
-        self._lock = threading.RLock()
-        # See issue #45: we need to be resilient when the locator is used
-        # in a thread, e.g. with concurrent.futures. We can't use self._lock
-        # as it is for coordinating our internal threads - the ones created
-        # in _prepare_threads.
-        self._gplock = threading.RLock()
-        self.platform_check = False  # See issue #112
-
-    def _prepare_threads(self):
-        """
-        Threads are created only when get_project is called, and terminate
-        before it returns. They are there primarily to parallelise I/O (i.e.
-        fetching web pages).
-        """
-        self._threads = []
-        for i in range(self.num_workers):
-            t = threading.Thread(target=self._fetch)
-            t.setDaemon(True)
-            t.start()
-            self._threads.append(t)
-
-    def _wait_threads(self):
-        """
-        Tell all the threads to terminate (by sending a sentinel value) and
-        wait for them to do so.
-        """
-        # Note that you need two loops, since you can't say which
-        # thread will get each sentinel
-        for t in self._threads:
-            self._to_fetch.put(None)    # sentinel
-        for t in self._threads:
-            t.join()
-        self._threads = []
-
-    def _get_project(self, name):
-        result = {'urls': {}, 'digests': {}}
-        with self._gplock:
-            self.result = result
-            self.project_name = name
-            url = urljoin(self.base_url, '%s/' % quote(name))
-            self._seen.clear()
-            self._page_cache.clear()
-            self._prepare_threads()
-            try:
-                logger.debug('Queueing %s', url)
-                self._to_fetch.put(url)
-                self._to_fetch.join()
-            finally:
-                self._wait_threads()
-            del self.result
-        return result
-
-    platform_dependent = re.compile(r'\b(linux_(i\d86|x86_64|arm\w+)|'
-                                    r'win(32|_amd64)|macosx_?\d+)\b', re.I)
-
-    def _is_platform_dependent(self, url):
-        """
-        Does an URL refer to a platform-specific download?
-        """
-        return self.platform_dependent.search(url)
-
-    def _process_download(self, url):
-        """
-        See if an URL is a suitable download for a project.
-
-        If it is, register information in the result dictionary (for
-        _get_project) about the specific version it's for.
-
-        Note that the return value isn't actually used other than as a boolean
-        value.
-        """
-        if self.platform_check and self._is_platform_dependent(url):
-            info = None
-        else:
-            info = self.convert_url_to_download_info(url, self.project_name)
-        logger.debug('process_download: %s -> %s', url, info)
-        if info:
-            with self._lock:    # needed because self.result is shared
-                self._update_version_data(self.result, info)
-        return info
-
-    def _should_queue(self, link, referrer, rel):
-        """
-        Determine whether a link URL from a referring page and with a
-        particular "rel" attribute should be queued for scraping.
-        """
-        scheme, netloc, path, _, _, _ = urlparse(link)
-        if path.endswith(self.source_extensions + self.binary_extensions +
-                         self.excluded_extensions):
-            result = False
-        elif self.skip_externals and not link.startswith(self.base_url):
-            result = False
-        elif not referrer.startswith(self.base_url):
-            result = False
-        elif rel not in ('homepage', 'download'):
-            result = False
-        elif scheme not in ('http', 'https', 'ftp'):
-            result = False
-        elif self._is_platform_dependent(link):
-            result = False
-        else:
-            host = netloc.split(':', 1)[0]
-            if host.lower() == 'localhost':
-                result = False
-            else:
-                result = True
-        logger.debug('should_queue: %s (%s) from %s -> %s', link, rel,
-                     referrer, result)
-        return result
-
-    def _fetch(self):
-        """
-        Get a URL to fetch from the work queue, get the HTML page, examine its
-        links for download candidates and candidates for further scraping.
-
-        This is a handy method to run in a thread.
-        """
-        while True:
-            url = self._to_fetch.get()
-            try:
-                if url:
-                    page = self.get_page(url)
-                    if page is None:    # e.g. after an error
-                        continue
-                    for link, rel in page.links:
-                        if link not in self._seen:
-                            try:
-                                self._seen.add(link)
-                                if (not self._process_download(link) and
-                                    self._should_queue(link, url, rel)):
-                                    logger.debug('Queueing %s from %s', link, url)
-                                    self._to_fetch.put(link)
-                            except MetadataInvalidError:  # e.g. invalid versions
-                                pass
-            except Exception as e:  # pragma: no cover
-                self.errors.put(text_type(e))
-            finally:
-                # always do this, to avoid hangs :-)
-                self._to_fetch.task_done()
-            if not url:
-                #logger.debug('Sentinel seen, quitting.')
-                break
-
-    def get_page(self, url):
-        """
-        Get the HTML for an URL, possibly from an in-memory cache.
-
-        XXX TODO Note: this cache is never actually cleared. It's assumed that
-        the data won't get stale over the lifetime of a locator instance (not
-        necessarily true for the default_locator).
-        """
-        # http://peak.telecommunity.com/DevCenter/EasyInstall#package-index-api
-        scheme, netloc, path, _, _, _ = urlparse(url)
-        if scheme == 'file' and os.path.isdir(url2pathname(path)):
-            url = urljoin(ensure_slash(url), 'index.html')
-
-        if url in self._page_cache:
-            result = self._page_cache[url]
-            logger.debug('Returning %s from cache: %s', url, result)
-        else:
-            host = netloc.split(':', 1)[0]
-            result = None
-            if host in self._bad_hosts:
-                logger.debug('Skipping %s due to bad host %s', url, host)
-            else:
-                req = Request(url, headers={'Accept-encoding': 'identity'})
-                try:
-                    logger.debug('Fetching %s', url)
-                    resp = self.opener.open(req, timeout=self.timeout)
-                    logger.debug('Fetched %s', url)
-                    headers = resp.info()
-                    content_type = headers.get('Content-Type', '')
-                    if HTML_CONTENT_TYPE.match(content_type):
-                        final_url = resp.geturl()
-                        data = resp.read()
-                        encoding = headers.get('Content-Encoding')
-                        if encoding:
-                            decoder = self.decoders[encoding]   # fail if not found
-                            data = decoder(data)
-                        encoding = 'utf-8'
-                        m = CHARSET.search(content_type)
-                        if m:
-                            encoding = m.group(1)
-                        try:
-                            data = data.decode(encoding)
-                        except UnicodeError:  # pragma: no cover
-                            data = data.decode('latin-1')    # fallback
-                        result = Page(data, final_url)
-                        self._page_cache[final_url] = result
-                except HTTPError as e:
-                    if e.code != 404:
-                        logger.exception('Fetch failed: %s: %s', url, e)
-                except URLError as e:  # pragma: no cover
-                    logger.exception('Fetch failed: %s: %s', url, e)
-                    with self._lock:
-                        self._bad_hosts.add(host)
-                except Exception as e:  # pragma: no cover
-                    logger.exception('Fetch failed: %s: %s', url, e)
-                finally:
-                    self._page_cache[url] = result   # even if None (failure)
-        return result
-
-    _distname_re = re.compile('<a href=[^>]*>([^<]+)<')
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        result = set()
-        page = self.get_page(self.base_url)
-        if not page:
-            raise DistlibException('Unable to get %s' % self.base_url)
-        for match in self._distname_re.finditer(page.data):
-            result.add(match.group(1))
-        return result
-
-class DirectoryLocator(Locator):
-    """
-    This class locates distributions in a directory tree.
-    """
-
-    def __init__(self, path, **kwargs):
-        """
-        Initialise an instance.
-        :param path: The root of the directory tree to search.
-        :param kwargs: Passed to the superclass constructor,
-                       except for:
-                       * recursive - if True (the default), subdirectories are
-                         recursed into. If False, only the top-level directory
-                         is searched,
-        """
-        self.recursive = kwargs.pop('recursive', True)
-        super(DirectoryLocator, self).__init__(**kwargs)
-        path = os.path.abspath(path)
-        if not os.path.isdir(path):  # pragma: no cover
-            raise DistlibException('Not a directory: %r' % path)
-        self.base_dir = path
-
-    def should_include(self, filename, parent):
-        """
-        Should a filename be considered as a candidate for a distribution
-        archive? As well as the filename, the directory which contains it
-        is provided, though not used by the current implementation.
-        """
-        return filename.endswith(self.downloadable_extensions)
-
-    def _get_project(self, name):
-        result = {'urls': {}, 'digests': {}}
-        for root, dirs, files in os.walk(self.base_dir):
-            for fn in files:
-                if self.should_include(fn, root):
-                    fn = os.path.join(root, fn)
-                    url = urlunparse(('file', '',
-                                      pathname2url(os.path.abspath(fn)),
-                                      '', '', ''))
-                    info = self.convert_url_to_download_info(url, name)
-                    if info:
-                        self._update_version_data(result, info)
-            if not self.recursive:
-                break
-        return result
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        result = set()
-        for root, dirs, files in os.walk(self.base_dir):
-            for fn in files:
-                if self.should_include(fn, root):
-                    fn = os.path.join(root, fn)
-                    url = urlunparse(('file', '',
-                                      pathname2url(os.path.abspath(fn)),
-                                      '', '', ''))
-                    info = self.convert_url_to_download_info(url, None)
-                    if info:
-                        result.add(info['name'])
-            if not self.recursive:
-                break
-        return result
-
-class JSONLocator(Locator):
-    """
-    This locator uses special extended metadata (not available on PyPI) and is
-    the basis of performant dependency resolution in distlib. Other locators
-    require archive downloads before dependencies can be determined! As you
-    might imagine, that can be slow.
-    """
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        raise NotImplementedError('Not available from this locator')
-
-    def _get_project(self, name):
-        result = {'urls': {}, 'digests': {}}
-        data = get_project_data(name)
-        if data:
-            for info in data.get('files', []):
-                if info['ptype'] != 'sdist' or info['pyversion'] != 'source':
-                    continue
-                # We don't store summary in project metadata as it makes
-                # the data bigger for no benefit during dependency
-                # resolution
-                dist = make_dist(data['name'], info['version'],
-                                 summary=data.get('summary',
-                                                  'Placeholder for summary'),
-                                 scheme=self.scheme)
-                md = dist.metadata
-                md.source_url = info['url']
-                # TODO SHA256 digest
-                if 'digest' in info and info['digest']:
-                    dist.digest = ('md5', info['digest'])
-                md.dependencies = info.get('requirements', {})
-                dist.exports = info.get('exports', {})
-                result[dist.version] = dist
-                result['urls'].setdefault(dist.version, set()).add(info['url'])
-        return result
-
-class DistPathLocator(Locator):
-    """
-    This locator finds installed distributions in a path. It can be useful for
-    adding to an :class:`AggregatingLocator`.
-    """
-    def __init__(self, distpath, **kwargs):
-        """
-        Initialise an instance.
-
-        :param distpath: A :class:`DistributionPath` instance to search.
-        """
-        super(DistPathLocator, self).__init__(**kwargs)
-        assert isinstance(distpath, DistributionPath)
-        self.distpath = distpath
-
-    def _get_project(self, name):
-        dist = self.distpath.get_distribution(name)
-        if dist is None:
-            result = {'urls': {}, 'digests': {}}
-        else:
-            result = {
-                dist.version: dist,
-                'urls': {dist.version: set([dist.source_url])},
-                'digests': {dist.version: set([None])}
-            }
-        return result
-
-
-class AggregatingLocator(Locator):
-    """
-    This class allows you to chain and/or merge a list of locators.
-    """
-    def __init__(self, *locators, **kwargs):
-        """
-        Initialise an instance.
-
-        :param locators: The list of locators to search.
-        :param kwargs: Passed to the superclass constructor,
-                       except for:
-                       * merge - if False (the default), the first successful
-                         search from any of the locators is returned. If True,
-                         the results from all locators are merged (this can be
-                         slow).
-        """
-        self.merge = kwargs.pop('merge', False)
-        self.locators = locators
-        super(AggregatingLocator, self).__init__(**kwargs)
-
-    def clear_cache(self):
-        super(AggregatingLocator, self).clear_cache()
-        for locator in self.locators:
-            locator.clear_cache()
-
-    def _set_scheme(self, value):
-        self._scheme = value
-        for locator in self.locators:
-            locator.scheme = value
-
-    scheme = property(Locator.scheme.fget, _set_scheme)
-
-    def _get_project(self, name):
-        result = {}
-        for locator in self.locators:
-            d = locator.get_project(name)
-            if d:
-                if self.merge:
-                    files = result.get('urls', {})
-                    digests = result.get('digests', {})
-                    # next line could overwrite result['urls'], result['digests']
-                    result.update(d)
-                    df = result.get('urls')
-                    if files and df:
-                        for k, v in files.items():
-                            if k in df:
-                                df[k] |= v
-                            else:
-                                df[k] = v
-                    dd = result.get('digests')
-                    if digests and dd:
-                        dd.update(digests)
-                else:
-                    # See issue #18. If any dists are found and we're looking
-                    # for specific constraints, we only return something if
-                    # a match is found. For example, if a DirectoryLocator
-                    # returns just foo (1.0) while we're looking for
-                    # foo (>= 2.0), we'll pretend there was nothing there so
-                    # that subsequent locators can be queried. Otherwise we
-                    # would just return foo (1.0) which would then lead to a
-                    # failure to find foo (>= 2.0), because other locators
-                    # weren't searched. Note that this only matters when
-                    # merge=False.
-                    if self.matcher is None:
-                        found = True
-                    else:
-                        found = False
-                        for k in d:
-                            if self.matcher.match(k):
-                                found = True
-                                break
-                    if found:
-                        result = d
-                        break
-        return result
-
-    def get_distribution_names(self):
-        """
-        Return all the distribution names known to this locator.
-        """
-        result = set()
-        for locator in self.locators:
-            try:
-                result |= locator.get_distribution_names()
-            except NotImplementedError:
-                pass
-        return result
-
-
-# We use a legacy scheme simply because most of the dists on PyPI use legacy
-# versions which don't conform to PEP 426 / PEP 440.
-default_locator = AggregatingLocator(
-                    JSONLocator(),
-                    SimpleScrapingLocator('https://pypi.org/simple/',
-                                          timeout=3.0),
-                    scheme='legacy')
-
-locate = default_locator.locate
-
-NAME_VERSION_RE = re.compile(r'(?P<name>[\w-]+)\s*'
-                             r'\(\s*(==\s*)?(?P<ver>[^)]+)\)$')
-
-class DependencyFinder(object):
-    """
-    Locate dependencies for distributions.
-    """
-
-    def __init__(self, locator=None):
-        """
-        Initialise an instance, using the specified locator
-        to locate distributions.
-        """
-        self.locator = locator or default_locator
-        self.scheme = get_scheme(self.locator.scheme)
-
-    def add_distribution(self, dist):
-        """
-        Add a distribution to the finder. This will update internal information
-        about who provides what.
-        :param dist: The distribution to add.
-        """
-        logger.debug('adding distribution %s', dist)
-        name = dist.key
-        self.dists_by_name[name] = dist
-        self.dists[(name, dist.version)] = dist
-        for p in dist.provides:
-            name, version = parse_name_and_version(p)
-            logger.debug('Add to provided: %s, %s, %s', name, version, dist)
-            self.provided.setdefault(name, set()).add((version, dist))
-
-    def remove_distribution(self, dist):
-        """
-        Remove a distribution from the finder. This will update internal
-        information about who provides what.
-        :param dist: The distribution to remove.
-        """
-        logger.debug('removing distribution %s', dist)
-        name = dist.key
-        del self.dists_by_name[name]
-        del self.dists[(name, dist.version)]
-        for p in dist.provides:
-            name, version = parse_name_and_version(p)
-            logger.debug('Remove from provided: %s, %s, %s', name, version, dist)
-            s = self.provided[name]
-            s.remove((version, dist))
-            if not s:
-                del self.provided[name]
-
-    def get_matcher(self, reqt):
-        """
-        Get a version matcher for a requirement.
-        :param reqt: The requirement
-        :type reqt: str
-        :return: A version matcher (an instance of
-                 :class:`distlib.version.Matcher`).
-        """
-        try:
-            matcher = self.scheme.matcher(reqt)
-        except UnsupportedVersionError:  # pragma: no cover
-            # XXX compat-mode if cannot read the version
-            name = reqt.split()[0]
-            matcher = self.scheme.matcher(name)
-        return matcher
-
-    def find_providers(self, reqt):
-        """
-        Find the distributions which can fulfill a requirement.
-
-        :param reqt: The requirement.
-         :type reqt: str
-        :return: A set of distribution which can fulfill the requirement.
-        """
-        matcher = self.get_matcher(reqt)
-        name = matcher.key   # case-insensitive
-        result = set()
-        provided = self.provided
-        if name in provided:
-            for version, provider in provided[name]:
-                try:
-                    match = matcher.match(version)
-                except UnsupportedVersionError:
-                    match = False
-
-                if match:
-                    result.add(provider)
-                    break
-        return result
-
-    def try_to_replace(self, provider, other, problems):
-        """
-        Attempt to replace one provider with another. This is typically used
-        when resolving dependencies from multiple sources, e.g. A requires
-        (B >= 1.0) while C requires (B >= 1.1).
-
-        For successful replacement, ``provider`` must meet all the requirements
-        which ``other`` fulfills.
-
-        :param provider: The provider we are trying to replace with.
-        :param other: The provider we're trying to replace.
-        :param problems: If False is returned, this will contain what
-                         problems prevented replacement. This is currently
-                         a tuple of the literal string 'cantreplace',
-                         ``provider``, ``other``  and the set of requirements
-                         that ``provider`` couldn't fulfill.
-        :return: True if we can replace ``other`` with ``provider``, else
-                 False.
-        """
-        rlist = self.reqts[other]
-        unmatched = set()
-        for s in rlist:
-            matcher = self.get_matcher(s)
-            if not matcher.match(provider.version):
-                unmatched.add(s)
-        if unmatched:
-            # can't replace other with provider
-            problems.add(('cantreplace', provider, other,
-                          frozenset(unmatched)))
-            result = False
-        else:
-            # can replace other with provider
-            self.remove_distribution(other)
-            del self.reqts[other]
-            for s in rlist:
-                self.reqts.setdefault(provider, set()).add(s)
-            self.add_distribution(provider)
-            result = True
-        return result
-
-    def find(self, requirement, meta_extras=None, prereleases=False):
-        """
-        Find a distribution and all distributions it depends on.
-
-        :param requirement: The requirement specifying the distribution to
-                            find, or a Distribution instance.
-        :param meta_extras: A list of meta extras such as :test:, :build: and
-                            so on.
-        :param prereleases: If ``True``, allow pre-release versions to be
-                            returned - otherwise, don't return prereleases
-                            unless they're all that's available.
-
-        Return a set of :class:`Distribution` instances and a set of
-        problems.
-
-        The distributions returned should be such that they have the
-        :attr:`required` attribute set to ``True`` if they were
-        from the ``requirement`` passed to ``find()``, and they have the
-        :attr:`build_time_dependency` attribute set to ``True`` unless they
-        are post-installation dependencies of the ``requirement``.
-
-        The problems should be a tuple consisting of the string
-        ``'unsatisfied'`` and the requirement which couldn't be satisfied
-        by any distribution known to the locator.
-        """
-
-        self.provided = {}
-        self.dists = {}
-        self.dists_by_name = {}
-        self.reqts = {}
-
-        meta_extras = set(meta_extras or [])
-        if ':*:' in meta_extras:
-            meta_extras.remove(':*:')
-            # :meta: and :run: are implicitly included
-            meta_extras |= set([':test:', ':build:', ':dev:'])
-
-        if isinstance(requirement, Distribution):
-            dist = odist = requirement
-            logger.debug('passed %s as requirement', odist)
-        else:
-            dist = odist = self.locator.locate(requirement,
-                                               prereleases=prereleases)
-            if dist is None:
-                raise DistlibException('Unable to locate %r' % requirement)
-            logger.debug('located %s', odist)
-        dist.requested = True
-        problems = set()
-        todo = set([dist])
-        install_dists = set([odist])
-        while todo:
-            dist = todo.pop()
-            name = dist.key     # case-insensitive
-            if name not in self.dists_by_name:
-                self.add_distribution(dist)
-            else:
-                #import pdb; pdb.set_trace()
-                other = self.dists_by_name[name]
-                if other != dist:
-                    self.try_to_replace(dist, other, problems)
-
-            ireqts = dist.run_requires | dist.meta_requires
-            sreqts = dist.build_requires
-            ereqts = set()
-            if meta_extras and dist in install_dists:
-                for key in ('test', 'build', 'dev'):
-                    e = ':%s:' % key
-                    if e in meta_extras:
-                        ereqts |= getattr(dist, '%s_requires' % key)
-            all_reqts = ireqts | sreqts | ereqts
-            for r in all_reqts:
-                providers = self.find_providers(r)
-                if not providers:
-                    logger.debug('No providers found for %r', r)
-                    provider = self.locator.locate(r, prereleases=prereleases)
-                    # If no provider is found and we didn't consider
-                    # prereleases, consider them now.
-                    if provider is None and not prereleases:
-                        provider = self.locator.locate(r, prereleases=True)
-                    if provider is None:
-                        logger.debug('Cannot satisfy %r', r)
-                        problems.add(('unsatisfied', r))
-                    else:
-                        n, v = provider.key, provider.version
-                        if (n, v) not in self.dists:
-                            todo.add(provider)
-                        providers.add(provider)
-                        if r in ireqts and dist in install_dists:
-                            install_dists.add(provider)
-                            logger.debug('Adding %s to install_dists',
-                                         provider.name_and_version)
-                for p in providers:
-                    name = p.key
-                    if name not in self.dists_by_name:
-                        self.reqts.setdefault(p, set()).add(r)
-                    else:
-                        other = self.dists_by_name[name]
-                        if other != p:
-                            # see if other can be replaced by p
-                            self.try_to_replace(p, other, problems)
-
-        dists = set(self.dists.values())
-        for dist in dists:
-            dist.build_time_dependency = dist not in install_dists
-            if dist.build_time_dependency:
-                logger.debug('%s is a build-time dependency only.',
-                             dist.name_and_version)
-        logger.debug('find done for %s', odist)
-        return dists, problems