--- a/lib/python3.8/site-packages/pip/_vendor/contextlib2.py	Mon Jul 27 03:47:31 2020 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,518 +0,0 @@
-"""contextlib2 - backports and enhancements to the contextlib module"""
-
-import abc
-import sys
-import warnings
-from collections import deque
-from functools import wraps
-
-__all__ = ["contextmanager", "closing", "nullcontext",
-           "AbstractContextManager",
-           "ContextDecorator", "ExitStack",
-           "redirect_stdout", "redirect_stderr", "suppress"]
-
-# Backwards compatibility
-__all__ += ["ContextStack"]
-
-
-# Backport abc.ABC
-if sys.version_info[:2] >= (3, 4):
-    _abc_ABC = abc.ABC
-else:
-    _abc_ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})
-
-
-# Backport classic class MRO
-def _classic_mro(C, result):
-    if C in result:
-        return
-    result.append(C)
-    for B in C.__bases__:
-        _classic_mro(B, result)
-    return result
-
-
-# Backport _collections_abc._check_methods
-def _check_methods(C, *methods):
-    try:
-        mro = C.__mro__
-    except AttributeError:
-        mro = tuple(_classic_mro(C, []))
-
-    for method in methods:
-        for B in mro:
-            if method in B.__dict__:
-                if B.__dict__[method] is None:
-                    return NotImplemented
-                break
-        else:
-            return NotImplemented
-    return True
-
-
-class AbstractContextManager(_abc_ABC):
-    """An abstract base class for context managers."""
-
-    def __enter__(self):
-        """Return `self` upon entering the runtime context."""
-        return self
-
-    @abc.abstractmethod
-    def __exit__(self, exc_type, exc_value, traceback):
-        """Raise any exception triggered within the runtime context."""
-        return None
-
-    @classmethod
-    def __subclasshook__(cls, C):
-        """Check whether subclass is considered a subclass of this ABC."""
-        if cls is AbstractContextManager:
-            return _check_methods(C, "__enter__", "__exit__")
-        return NotImplemented
-
-
-class ContextDecorator(object):
-    """A base class or mixin that enables context managers to work as decorators."""
-
-    def refresh_cm(self):
-        """Returns the context manager used to actually wrap the call to the
-        decorated function.
-
-        The default implementation just returns *self*.
-
-        Overriding this method allows otherwise one-shot context managers
-        like _GeneratorContextManager to support use as decorators via
-        implicit recreation.
-
-        DEPRECATED: refresh_cm was never added to the standard library's
-                    ContextDecorator API
-        """
-        warnings.warn("refresh_cm was never added to the standard library",
-                      DeprecationWarning)
-        return self._recreate_cm()
-
-    def _recreate_cm(self):
-        """Return a recreated instance of self.
-
-        Allows an otherwise one-shot context manager like
-        _GeneratorContextManager to support use as
-        a decorator via implicit recreation.
-
-        This is a private interface just for _GeneratorContextManager.
-        See issue #11647 for details.
-        """
-        return self
-
-    def __call__(self, func):
-        @wraps(func)
-        def inner(*args, **kwds):
-            with self._recreate_cm():
-                return func(*args, **kwds)
-        return inner
-
-
-class _GeneratorContextManager(ContextDecorator):
-    """Helper for @contextmanager decorator."""
-
-    def __init__(self, func, args, kwds):
-        self.gen = func(*args, **kwds)
-        self.func, self.args, self.kwds = func, args, kwds
-        # Issue 19330: ensure context manager instances have good docstrings
-        doc = getattr(func, "__doc__", None)
-        if doc is None:
-            doc = type(self).__doc__
-        self.__doc__ = doc
-        # Unfortunately, this still doesn't provide good help output when
-        # inspecting the created context manager instances, since pydoc
-        # currently bypasses the instance docstring and shows the docstring
-        # for the class instead.
-        # See http://bugs.python.org/issue19404 for more details.
-
-    def _recreate_cm(self):
-        # _GCM instances are one-shot context managers, so the
-        # CM must be recreated each time a decorated function is
-        # called
-        return self.__class__(self.func, self.args, self.kwds)
-
-    def __enter__(self):
-        try:
-            return next(self.gen)
-        except StopIteration:
-            raise RuntimeError("generator didn't yield")
-
-    def __exit__(self, type, value, traceback):
-        if type is None:
-            try:
-                next(self.gen)
-            except StopIteration:
-                return
-            else:
-                raise RuntimeError("generator didn't stop")
-        else:
-            if value is None:
-                # Need to force instantiation so we can reliably
-                # tell if we get the same exception back
-                value = type()
-            try:
-                self.gen.throw(type, value, traceback)
-                raise RuntimeError("generator didn't stop after throw()")
-            except StopIteration as exc:
-                # Suppress StopIteration *unless* it's the same exception that
-                # was passed to throw().  This prevents a StopIteration
-                # raised inside the "with" statement from being suppressed.
-                return exc is not value
-            except RuntimeError as exc:
-                # Don't re-raise the passed in exception
-                if exc is value:
-                    return False
-                # Likewise, avoid suppressing if a StopIteration exception
-                # was passed to throw() and later wrapped into a RuntimeError
-                # (see PEP 479).
-                if _HAVE_EXCEPTION_CHAINING and exc.__cause__ is value:
-                    return False
-                raise
-            except:
-                # only re-raise if it's *not* the exception that was
-                # passed to throw(), because __exit__() must not raise
-                # an exception unless __exit__() itself failed.  But throw()
-                # has to raise the exception to signal propagation, so this
-                # fixes the impedance mismatch between the throw() protocol
-                # and the __exit__() protocol.
-                #
-                if sys.exc_info()[1] is not value:
-                    raise
-
-
-def contextmanager(func):
-    """@contextmanager decorator.
-
-    Typical usage:
-
-        @contextmanager
-        def some_generator(<arguments>):
-            <setup>
-            try:
-                yield <value>
-            finally:
-                <cleanup>
-
-    This makes this:
-
-        with some_generator(<arguments>) as <variable>:
-            <body>
-
-    equivalent to this:
-
-        <setup>
-        try:
-            <variable> = <value>
-            <body>
-        finally:
-            <cleanup>
-
-    """
-    @wraps(func)
-    def helper(*args, **kwds):
-        return _GeneratorContextManager(func, args, kwds)
-    return helper
-
-
-class closing(object):
-    """Context to automatically close something at the end of a block.
-
-    Code like this:
-
-        with closing(<module>.open(<arguments>)) as f:
-            <block>
-
-    is equivalent to this:
-
-        f = <module>.open(<arguments>)
-        try:
-            <block>
-        finally:
-            f.close()
-
-    """
-    def __init__(self, thing):
-        self.thing = thing
-
-    def __enter__(self):
-        return self.thing
-
-    def __exit__(self, *exc_info):
-        self.thing.close()
-
-
-class _RedirectStream(object):
-
-    _stream = None
-
-    def __init__(self, new_target):
-        self._new_target = new_target
-        # We use a list of old targets to make this CM re-entrant
-        self._old_targets = []
-
-    def __enter__(self):
-        self._old_targets.append(getattr(sys, self._stream))
-        setattr(sys, self._stream, self._new_target)
-        return self._new_target
-
-    def __exit__(self, exctype, excinst, exctb):
-        setattr(sys, self._stream, self._old_targets.pop())
-
-
-class redirect_stdout(_RedirectStream):
-    """Context manager for temporarily redirecting stdout to another file.
-
-        # How to send help() to stderr
-        with redirect_stdout(sys.stderr):
-            help(dir)
-
-        # How to write help() to a file
-        with open('help.txt', 'w') as f:
-            with redirect_stdout(f):
-                help(pow)
-    """
-
-    _stream = "stdout"
-
-
-class redirect_stderr(_RedirectStream):
-    """Context manager for temporarily redirecting stderr to another file."""
-
-    _stream = "stderr"
-
-
-class suppress(object):
-    """Context manager to suppress specified exceptions
-
-    After the exception is suppressed, execution proceeds with the next
-    statement following the with statement.
-
-         with suppress(FileNotFoundError):
-             os.remove(somefile)
-         # Execution still resumes here if the file was already removed
-    """
-
-    def __init__(self, *exceptions):
-        self._exceptions = exceptions
-
-    def __enter__(self):
-        pass
-
-    def __exit__(self, exctype, excinst, exctb):
-        # Unlike isinstance and issubclass, CPython exception handling
-        # currently only looks at the concrete type hierarchy (ignoring
-        # the instance and subclass checking hooks). While Guido considers
-        # that a bug rather than a feature, it's a fairly hard one to fix
-        # due to various internal implementation details. suppress provides
-        # the simpler issubclass based semantics, rather than trying to
-        # exactly reproduce the limitations of the CPython interpreter.
-        #
-        # See http://bugs.python.org/issue12029 for more details
-        return exctype is not None and issubclass(exctype, self._exceptions)
-
-
-# Context manipulation is Python 3 only
-_HAVE_EXCEPTION_CHAINING = sys.version_info[0] >= 3
-if _HAVE_EXCEPTION_CHAINING:
-    def _make_context_fixer(frame_exc):
-        def _fix_exception_context(new_exc, old_exc):
-            # Context may not be correct, so find the end of the chain
-            while 1:
-                exc_context = new_exc.__context__
-                if exc_context is old_exc:
-                    # Context is already set correctly (see issue 20317)
-                    return
-                if exc_context is None or exc_context is frame_exc:
-                    break
-                new_exc = exc_context
-            # Change the end of the chain to point to the exception
-            # we expect it to reference
-            new_exc.__context__ = old_exc
-        return _fix_exception_context
-
-    def _reraise_with_existing_context(exc_details):
-        try:
-            # bare "raise exc_details[1]" replaces our carefully
-            # set-up context
-            fixed_ctx = exc_details[1].__context__
-            raise exc_details[1]
-        except BaseException:
-            exc_details[1].__context__ = fixed_ctx
-            raise
-else:
-    # No exception context in Python 2
-    def _make_context_fixer(frame_exc):
-        return lambda new_exc, old_exc: None
-
-    # Use 3 argument raise in Python 2,
-    # but use exec to avoid SyntaxError in Python 3
-    def _reraise_with_existing_context(exc_details):
-        exc_type, exc_value, exc_tb = exc_details
-        exec("raise exc_type, exc_value, exc_tb")
-
-# Handle old-style classes if they exist
-try:
-    from types import InstanceType
-except ImportError:
-    # Python 3 doesn't have old-style classes
-    _get_type = type
-else:
-    # Need to handle old-style context managers on Python 2
-    def _get_type(obj):
-        obj_type = type(obj)
-        if obj_type is InstanceType:
-            return obj.__class__  # Old-style class
-        return obj_type  # New-style class
-
-
-# Inspired by discussions on http://bugs.python.org/issue13585
-class ExitStack(object):
-    """Context manager for dynamic management of a stack of exit callbacks
-
-    For example:
-
-        with ExitStack() as stack:
-            files = [stack.enter_context(open(fname)) for fname in filenames]
-            # All opened files will automatically be closed at the end of
-            # the with statement, even if attempts to open files later
-            # in the list raise an exception
-
-    """
-    def __init__(self):
-        self._exit_callbacks = deque()
-
-    def pop_all(self):
-        """Preserve the context stack by transferring it to a new instance"""
-        new_stack = type(self)()
-        new_stack._exit_callbacks = self._exit_callbacks
-        self._exit_callbacks = deque()
-        return new_stack
-
-    def _push_cm_exit(self, cm, cm_exit):
-        """Helper to correctly register callbacks to __exit__ methods"""
-        def _exit_wrapper(*exc_details):
-            return cm_exit(cm, *exc_details)
-        _exit_wrapper.__self__ = cm
-        self.push(_exit_wrapper)
-
-    def push(self, exit):
-        """Registers a callback with the standard __exit__ method signature
-
-        Can suppress exceptions the same way __exit__ methods can.
-
-        Also accepts any object with an __exit__ method (registering a call
-        to the method instead of the object itself)
-        """
-        # We use an unbound method rather than a bound method to follow
-        # the standard lookup behaviour for special methods
-        _cb_type = _get_type(exit)
-        try:
-            exit_method = _cb_type.__exit__
-        except AttributeError:
-            # Not a context manager, so assume its a callable
-            self._exit_callbacks.append(exit)
-        else:
-            self._push_cm_exit(exit, exit_method)
-        return exit # Allow use as a decorator
-
-    def callback(self, callback, *args, **kwds):
-        """Registers an arbitrary callback and arguments.
-
-        Cannot suppress exceptions.
-        """
-        def _exit_wrapper(exc_type, exc, tb):
-            callback(*args, **kwds)
-        # We changed the signature, so using @wraps is not appropriate, but
-        # setting __wrapped__ may still help with introspection
-        _exit_wrapper.__wrapped__ = callback
-        self.push(_exit_wrapper)
-        return callback # Allow use as a decorator
-
-    def enter_context(self, cm):
-        """Enters the supplied context manager
-
-        If successful, also pushes its __exit__ method as a callback and
-        returns the result of the __enter__ method.
-        """
-        # We look up the special methods on the type to match the with statement
-        _cm_type = _get_type(cm)
-        _exit = _cm_type.__exit__
-        result = _cm_type.__enter__(cm)
-        self._push_cm_exit(cm, _exit)
-        return result
-
-    def close(self):
-        """Immediately unwind the context stack"""
-        self.__exit__(None, None, None)
-
-    def __enter__(self):
-        return self
-
-    def __exit__(self, *exc_details):
-        received_exc = exc_details[0] is not None
-
-        # We manipulate the exception state so it behaves as though
-        # we were actually nesting multiple with statements
-        frame_exc = sys.exc_info()[1]
-        _fix_exception_context = _make_context_fixer(frame_exc)
-
-        # Callbacks are invoked in LIFO order to match the behaviour of
-        # nested context managers
-        suppressed_exc = False
-        pending_raise = False
-        while self._exit_callbacks:
-            cb = self._exit_callbacks.pop()
-            try:
-                if cb(*exc_details):
-                    suppressed_exc = True
-                    pending_raise = False
-                    exc_details = (None, None, None)
-            except:
-                new_exc_details = sys.exc_info()
-                # simulate the stack of exceptions by setting the context
-                _fix_exception_context(new_exc_details[1], exc_details[1])
-                pending_raise = True
-                exc_details = new_exc_details
-        if pending_raise:
-            _reraise_with_existing_context(exc_details)
-        return received_exc and suppressed_exc
-
-
-# Preserve backwards compatibility
-class ContextStack(ExitStack):
-    """Backwards compatibility alias for ExitStack"""
-
-    def __init__(self):
-        warnings.warn("ContextStack has been renamed to ExitStack",
-                      DeprecationWarning)
-        super(ContextStack, self).__init__()
-
-    def register_exit(self, callback):
-        return self.push(callback)
-
-    def register(self, callback, *args, **kwds):
-        return self.callback(callback, *args, **kwds)
-
-    def preserve(self):
-        return self.pop_all()
-
-
-class nullcontext(AbstractContextManager):
-    """Context manager that does no additional processing.
-    Used as a stand-in for a normal context manager, when a particular
-    block of code is only sometimes used with a normal context manager:
-    cm = optional_cm if condition else nullcontext()
-    with cm:
-        # Perform operation, using optional_cm if condition is True
-    """
-
-    def __init__(self, enter_result=None):
-        self.enter_result = enter_result
-
-    def __enter__(self):
-        return self.enter_result
-
-    def __exit__(self, *excinfo):
-        pass