--- a/lib/python3.8/site-packages/pip/_internal/req/req_tracker.py	Mon Jul 27 03:47:31 2020 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,150 +0,0 @@
-# The following comment should be removed at some point in the future.
-# mypy: strict-optional=False
-
-from __future__ import absolute_import
-
-import contextlib
-import errno
-import hashlib
-import logging
-import os
-
-from pip._vendor import contextlib2
-
-from pip._internal.utils.temp_dir import TempDirectory
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
-
-if MYPY_CHECK_RUNNING:
-    from types import TracebackType
-    from typing import Dict, Iterator, Optional, Set, Type, Union
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.models.link import Link
-
-logger = logging.getLogger(__name__)
-
-
-@contextlib.contextmanager
-def update_env_context_manager(**changes):
-    # type: (str) -> Iterator[None]
-    target = os.environ
-
-    # Save values from the target and change them.
-    non_existent_marker = object()
-    saved_values = {}  # type: Dict[str, Union[object, str]]
-    for name, new_value in changes.items():
-        try:
-            saved_values[name] = target[name]
-        except KeyError:
-            saved_values[name] = non_existent_marker
-        target[name] = new_value
-
-    try:
-        yield
-    finally:
-        # Restore original values in the target.
-        for name, original_value in saved_values.items():
-            if original_value is non_existent_marker:
-                del target[name]
-            else:
-                assert isinstance(original_value, str)  # for mypy
-                target[name] = original_value
-
-
-@contextlib.contextmanager
-def get_requirement_tracker():
-    # type: () -> Iterator[RequirementTracker]
-    root = os.environ.get('PIP_REQ_TRACKER')
-    with contextlib2.ExitStack() as ctx:
-        if root is None:
-            root = ctx.enter_context(
-                TempDirectory(kind='req-tracker')
-            ).path
-            ctx.enter_context(update_env_context_manager(PIP_REQ_TRACKER=root))
-            logger.debug("Initialized build tracking at %s", root)
-
-        with RequirementTracker(root) as tracker:
-            yield tracker
-
-
-class RequirementTracker(object):
-
-    def __init__(self, root):
-        # type: (str) -> None
-        self._root = root
-        self._entries = set()  # type: Set[InstallRequirement]
-        logger.debug("Created build tracker: %s", self._root)
-
-    def __enter__(self):
-        # type: () -> RequirementTracker
-        logger.debug("Entered build tracker: %s", self._root)
-        return self
-
-    def __exit__(
-        self,
-        exc_type,  # type: Optional[Type[BaseException]]
-        exc_val,  # type: Optional[BaseException]
-        exc_tb  # type: Optional[TracebackType]
-    ):
-        # type: (...) -> None
-        self.cleanup()
-
-    def _entry_path(self, link):
-        # type: (Link) -> str
-        hashed = hashlib.sha224(link.url_without_fragment.encode()).hexdigest()
-        return os.path.join(self._root, hashed)
-
-    def add(self, req):
-        # type: (InstallRequirement) -> None
-        """Add an InstallRequirement to build tracking.
-        """
-
-        # Get the file to write information about this requirement.
-        entry_path = self._entry_path(req.link)
-
-        # Try reading from the file. If it exists and can be read from, a build
-        # is already in progress, so a LookupError is raised.
-        try:
-            with open(entry_path) as fp:
-                contents = fp.read()
-        except IOError as e:
-            # if the error is anything other than "file does not exist", raise.
-            if e.errno != errno.ENOENT:
-                raise
-        else:
-            message = '%s is already being built: %s' % (req.link, contents)
-            raise LookupError(message)
-
-        # If we're here, req should really not be building already.
-        assert req not in self._entries
-
-        # Start tracking this requirement.
-        with open(entry_path, 'w') as fp:
-            fp.write(str(req))
-        self._entries.add(req)
-
-        logger.debug('Added %s to build tracker %r', req, self._root)
-
-    def remove(self, req):
-        # type: (InstallRequirement) -> None
-        """Remove an InstallRequirement from build tracking.
-        """
-
-        # Delete the created file and the corresponding entries.
-        os.unlink(self._entry_path(req.link))
-        self._entries.remove(req)
-
-        logger.debug('Removed %s from build tracker %r', req, self._root)
-
-    def cleanup(self):
-        # type: () -> None
-        for req in set(self._entries):
-            self.remove(req)
-
-        logger.debug("Removed build tracker: %r", self._root)
-
-    @contextlib.contextmanager
-    def track(self, req):
-        # type: (InstallRequirement) -> Iterator[None]
-        self.add(req)
-        yield
-        self.remove(req)