--- a/lib/python3.8/site-packages/pip/_internal/pyproject.py	Mon Jul 27 03:47:31 2020 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,196 +0,0 @@
-from __future__ import absolute_import
-
-import io
-import os
-import sys
-from collections import namedtuple
-
-from pip._vendor import pytoml, six
-from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
-
-from pip._internal.exceptions import InstallationError
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
-
-if MYPY_CHECK_RUNNING:
-    from typing import Any, Optional, List
-
-
-def _is_list_of_str(obj):
-    # type: (Any) -> bool
-    return (
-        isinstance(obj, list) and
-        all(isinstance(item, six.string_types) for item in obj)
-    )
-
-
-def make_pyproject_path(unpacked_source_directory):
-    # type: (str) -> str
-    path = os.path.join(unpacked_source_directory, 'pyproject.toml')
-
-    # Python2 __file__ should not be unicode
-    if six.PY2 and isinstance(path, six.text_type):
-        path = path.encode(sys.getfilesystemencoding())
-
-    return path
-
-
-BuildSystemDetails = namedtuple('BuildSystemDetails', [
-    'requires', 'backend', 'check', 'backend_path'
-])
-
-
-def load_pyproject_toml(
-    use_pep517,  # type: Optional[bool]
-    pyproject_toml,  # type: str
-    setup_py,  # type: str
-    req_name  # type: str
-):
-    # type: (...) -> Optional[BuildSystemDetails]
-    """Load the pyproject.toml file.
-
-    Parameters:
-        use_pep517 - Has the user requested PEP 517 processing? None
-                     means the user hasn't explicitly specified.
-        pyproject_toml - Location of the project's pyproject.toml file
-        setup_py - Location of the project's setup.py file
-        req_name - The name of the requirement we're processing (for
-                   error reporting)
-
-    Returns:
-        None if we should use the legacy code path, otherwise a tuple
-        (
-            requirements from pyproject.toml,
-            name of PEP 517 backend,
-            requirements we should check are installed after setting
-                up the build environment
-            directory paths to import the backend from (backend-path),
-                relative to the project root.
-        )
-    """
-    has_pyproject = os.path.isfile(pyproject_toml)
-    has_setup = os.path.isfile(setup_py)
-
-    if has_pyproject:
-        with io.open(pyproject_toml, encoding="utf-8") as f:
-            pp_toml = pytoml.load(f)
-        build_system = pp_toml.get("build-system")
-    else:
-        build_system = None
-
-    # The following cases must use PEP 517
-    # We check for use_pep517 being non-None and falsey because that means
-    # the user explicitly requested --no-use-pep517.  The value 0 as
-    # opposed to False can occur when the value is provided via an
-    # environment variable or config file option (due to the quirk of
-    # strtobool() returning an integer in pip's configuration code).
-    if has_pyproject and not has_setup:
-        if use_pep517 is not None and not use_pep517:
-            raise InstallationError(
-                "Disabling PEP 517 processing is invalid: "
-                "project does not have a setup.py"
-            )
-        use_pep517 = True
-    elif build_system and "build-backend" in build_system:
-        if use_pep517 is not None and not use_pep517:
-            raise InstallationError(
-                "Disabling PEP 517 processing is invalid: "
-                "project specifies a build backend of {} "
-                "in pyproject.toml".format(
-                    build_system["build-backend"]
-                )
-            )
-        use_pep517 = True
-
-    # If we haven't worked out whether to use PEP 517 yet,
-    # and the user hasn't explicitly stated a preference,
-    # we do so if the project has a pyproject.toml file.
-    elif use_pep517 is None:
-        use_pep517 = has_pyproject
-
-    # At this point, we know whether we're going to use PEP 517.
-    assert use_pep517 is not None
-
-    # If we're using the legacy code path, there is nothing further
-    # for us to do here.
-    if not use_pep517:
-        return None
-
-    if build_system is None:
-        # Either the user has a pyproject.toml with no build-system
-        # section, or the user has no pyproject.toml, but has opted in
-        # explicitly via --use-pep517.
-        # In the absence of any explicit backend specification, we
-        # assume the setuptools backend that most closely emulates the
-        # traditional direct setup.py execution, and require wheel and
-        # a version of setuptools that supports that backend.
-
-        build_system = {
-            "requires": ["setuptools>=40.8.0", "wheel"],
-            "build-backend": "setuptools.build_meta:__legacy__",
-        }
-
-    # If we're using PEP 517, we have build system information (either
-    # from pyproject.toml, or defaulted by the code above).
-    # Note that at this point, we do not know if the user has actually
-    # specified a backend, though.
-    assert build_system is not None
-
-    # Ensure that the build-system section in pyproject.toml conforms
-    # to PEP 518.
-    error_template = (
-        "{package} has a pyproject.toml file that does not comply "
-        "with PEP 518: {reason}"
-    )
-
-    # Specifying the build-system table but not the requires key is invalid
-    if "requires" not in build_system:
-        raise InstallationError(
-            error_template.format(package=req_name, reason=(
-                "it has a 'build-system' table but not "
-                "'build-system.requires' which is mandatory in the table"
-            ))
-        )
-
-    # Error out if requires is not a list of strings
-    requires = build_system["requires"]
-    if not _is_list_of_str(requires):
-        raise InstallationError(error_template.format(
-            package=req_name,
-            reason="'build-system.requires' is not a list of strings.",
-        ))
-
-    # Each requirement must be valid as per PEP 508
-    for requirement in requires:
-        try:
-            Requirement(requirement)
-        except InvalidRequirement:
-            raise InstallationError(
-                error_template.format(
-                    package=req_name,
-                    reason=(
-                        "'build-system.requires' contains an invalid "
-                        "requirement: {!r}".format(requirement)
-                    ),
-                )
-            )
-
-    backend = build_system.get("build-backend")
-    backend_path = build_system.get("backend-path", [])
-    check = []  # type: List[str]
-    if backend is None:
-        # If the user didn't specify a backend, we assume they want to use
-        # the setuptools backend. But we can't be sure they have included
-        # a version of setuptools which supplies the backend, or wheel
-        # (which is needed by the backend) in their requirements. So we
-        # make a note to check that those requirements are present once
-        # we have set up the environment.
-        # This is quite a lot of work to check for a very specific case. But
-        # the problem is, that case is potentially quite common - projects that
-        # adopted PEP 518 early for the ability to specify requirements to
-        # execute setup.py, but never considered needing to mention the build
-        # tools themselves. The original PEP 518 code had a similar check (but
-        # implemented in a different way).
-        backend = "setuptools.build_meta:__legacy__"
-        check = ["setuptools>=40.8.0", "wheel"]
-
-    return BuildSystemDetails(requires, backend, check, backend_path)