--- a/lib/python3.8/site-packages/pip/_internal/build_env.py	Mon Jul 27 03:47:31 2020 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,221 +0,0 @@
-"""Build Environment used for isolation during sdist building
-"""
-
-# The following comment should be removed at some point in the future.
-# mypy: strict-optional=False
-# mypy: disallow-untyped-defs=False
-
-import logging
-import os
-import sys
-import textwrap
-from collections import OrderedDict
-from distutils.sysconfig import get_python_lib
-from sysconfig import get_paths
-
-from pip._vendor.pkg_resources import Requirement, VersionConflict, WorkingSet
-
-from pip import __file__ as pip_location
-from pip._internal.utils.subprocess import call_subprocess
-from pip._internal.utils.temp_dir import TempDirectory
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
-from pip._internal.utils.ui import open_spinner
-
-if MYPY_CHECK_RUNNING:
-    from typing import Tuple, Set, Iterable, Optional, List
-    from pip._internal.index.package_finder import PackageFinder
-
-logger = logging.getLogger(__name__)
-
-
-class _Prefix:
-
-    def __init__(self, path):
-        # type: (str) -> None
-        self.path = path
-        self.setup = False
-        self.bin_dir = get_paths(
-            'nt' if os.name == 'nt' else 'posix_prefix',
-            vars={'base': path, 'platbase': path}
-        )['scripts']
-        # Note: prefer distutils' sysconfig to get the
-        # library paths so PyPy is correctly supported.
-        purelib = get_python_lib(plat_specific=False, prefix=path)
-        platlib = get_python_lib(plat_specific=True, prefix=path)
-        if purelib == platlib:
-            self.lib_dirs = [purelib]
-        else:
-            self.lib_dirs = [purelib, platlib]
-
-
-class BuildEnvironment(object):
-    """Creates and manages an isolated environment to install build deps
-    """
-
-    def __init__(self):
-        # type: () -> None
-        self._temp_dir = TempDirectory(kind="build-env")
-
-        self._prefixes = OrderedDict((
-            (name, _Prefix(os.path.join(self._temp_dir.path, name)))
-            for name in ('normal', 'overlay')
-        ))
-
-        self._bin_dirs = []  # type: List[str]
-        self._lib_dirs = []  # type: List[str]
-        for prefix in reversed(list(self._prefixes.values())):
-            self._bin_dirs.append(prefix.bin_dir)
-            self._lib_dirs.extend(prefix.lib_dirs)
-
-        # Customize site to:
-        # - ensure .pth files are honored
-        # - prevent access to system site packages
-        system_sites = {
-            os.path.normcase(site) for site in (
-                get_python_lib(plat_specific=False),
-                get_python_lib(plat_specific=True),
-            )
-        }
-        self._site_dir = os.path.join(self._temp_dir.path, 'site')
-        if not os.path.exists(self._site_dir):
-            os.mkdir(self._site_dir)
-        with open(os.path.join(self._site_dir, 'sitecustomize.py'), 'w') as fp:
-            fp.write(textwrap.dedent(
-                '''
-                import os, site, sys
-
-                # First, drop system-sites related paths.
-                original_sys_path = sys.path[:]
-                known_paths = set()
-                for path in {system_sites!r}:
-                    site.addsitedir(path, known_paths=known_paths)
-                system_paths = set(
-                    os.path.normcase(path)
-                    for path in sys.path[len(original_sys_path):]
-                )
-                original_sys_path = [
-                    path for path in original_sys_path
-                    if os.path.normcase(path) not in system_paths
-                ]
-                sys.path = original_sys_path
-
-                # Second, add lib directories.
-                # ensuring .pth file are processed.
-                for path in {lib_dirs!r}:
-                    assert not path in sys.path
-                    site.addsitedir(path)
-                '''
-            ).format(system_sites=system_sites, lib_dirs=self._lib_dirs))
-
-    def __enter__(self):
-        self._save_env = {
-            name: os.environ.get(name, None)
-            for name in ('PATH', 'PYTHONNOUSERSITE', 'PYTHONPATH')
-        }
-
-        path = self._bin_dirs[:]
-        old_path = self._save_env['PATH']
-        if old_path:
-            path.extend(old_path.split(os.pathsep))
-
-        pythonpath = [self._site_dir]
-
-        os.environ.update({
-            'PATH': os.pathsep.join(path),
-            'PYTHONNOUSERSITE': '1',
-            'PYTHONPATH': os.pathsep.join(pythonpath),
-        })
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        for varname, old_value in self._save_env.items():
-            if old_value is None:
-                os.environ.pop(varname, None)
-            else:
-                os.environ[varname] = old_value
-
-    def cleanup(self):
-        # type: () -> None
-        self._temp_dir.cleanup()
-
-    def check_requirements(self, reqs):
-        # type: (Iterable[str]) -> Tuple[Set[Tuple[str, str]], Set[str]]
-        """Return 2 sets:
-            - conflicting requirements: set of (installed, wanted) reqs tuples
-            - missing requirements: set of reqs
-        """
-        missing = set()
-        conflicting = set()
-        if reqs:
-            ws = WorkingSet(self._lib_dirs)
-            for req in reqs:
-                try:
-                    if ws.find(Requirement.parse(req)) is None:
-                        missing.add(req)
-                except VersionConflict as e:
-                    conflicting.add((str(e.args[0].as_requirement()),
-                                     str(e.args[1])))
-        return conflicting, missing
-
-    def install_requirements(
-        self,
-        finder,  # type: PackageFinder
-        requirements,  # type: Iterable[str]
-        prefix_as_string,  # type: str
-        message  # type: Optional[str]
-    ):
-        # type: (...) -> None
-        prefix = self._prefixes[prefix_as_string]
-        assert not prefix.setup
-        prefix.setup = True
-        if not requirements:
-            return
-        args = [
-            sys.executable, os.path.dirname(pip_location), 'install',
-            '--ignore-installed', '--no-user', '--prefix', prefix.path,
-            '--no-warn-script-location',
-        ]  # type: List[str]
-        if logger.getEffectiveLevel() <= logging.DEBUG:
-            args.append('-v')
-        for format_control in ('no_binary', 'only_binary'):
-            formats = getattr(finder.format_control, format_control)
-            args.extend(('--' + format_control.replace('_', '-'),
-                         ','.join(sorted(formats or {':none:'}))))
-
-        index_urls = finder.index_urls
-        if index_urls:
-            args.extend(['-i', index_urls[0]])
-            for extra_index in index_urls[1:]:
-                args.extend(['--extra-index-url', extra_index])
-        else:
-            args.append('--no-index')
-        for link in finder.find_links:
-            args.extend(['--find-links', link])
-
-        for host in finder.trusted_hosts:
-            args.extend(['--trusted-host', host])
-        if finder.allow_all_prereleases:
-            args.append('--pre')
-        args.append('--')
-        args.extend(requirements)
-        with open_spinner(message) as spinner:
-            call_subprocess(args, spinner=spinner)
-
-
-class NoOpBuildEnvironment(BuildEnvironment):
-    """A no-op drop-in replacement for BuildEnvironment
-    """
-
-    def __init__(self):
-        pass
-
-    def __enter__(self):
-        pass
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        pass
-
-    def cleanup(self):
-        pass
-
-    def install_requirements(self, finder, requirements, prefix, message):
-        raise NotImplementedError()