Update pip to 20.3

[pyup-bot]

This PR updates pip from 20.0.2 to 20.3.

Changelog

20.3

- Introduce a new ResolutionImpossible error, raised when pip encounters un-satisfiable dependency conflicts (`8546 <https://github.com/pypa/pip/issues/8546>`_, `8377 <https://github.com/pypa/pip/issues/8377>`_)
- Add a subcommand ``debug`` to ``pip config`` to list available configuration sources and the key-value pairs defined in them. (`6741 <https://github.com/pypa/pip/issues/6741>`_)
- Warn if index pages have unexpected content-type (`6754 <https://github.com/pypa/pip/issues/6754>`_)
- Allow specifying ``--prefer-binary`` option in a requirements file (`7693 <https://github.com/pypa/pip/issues/7693>`_)
- Generate PEP 376 REQUESTED metadata for user supplied requirements installed
by pip. (`7811 <https://github.com/pypa/pip/issues/7811>`_)
- Warn if package url is a vcs or an archive url with invalid scheme (`8128 <https://github.com/pypa/pip/issues/8128>`_)
- Parallelize network operations in ``pip list``. (`8504 <https://github.com/pypa/pip/issues/8504>`_)
- Allow the new resolver to obtain dependency information through wheels
lazily downloaded using HTTP range requests.  To enable this feature,
invoke ``pip`` with ``--use-feature=fast-deps``. (`8588 <https://github.com/pypa/pip/issues/8588>`_)
- Support ``--use-feature`` in requirements files (`8601 <https://github.com/pypa/pip/issues/8601>`_)

Bug Fixes
---------

- Use canonical package names while looking up already installed packages. (`5021 <https://github.com/pypa/pip/issues/5021>`_)
- Fix normalizing path on Windows when installing package on another logical disk. (`7625 <https://github.com/pypa/pip/issues/7625>`_)
- The VCS commands run by pip as subprocesses don't merge stdout and stderr anymore, improving the output parsing by subsequent commands. (`7968 <https://github.com/pypa/pip/issues/7968>`_)
- Correctly treat non-ASCII entry point declarations in wheels so they can be
installed on Windows. (`8342 <https://github.com/pypa/pip/issues/8342>`_)
- Update author email in config and tests to reflect decommissioning of pypa-dev list. (`8454 <https://github.com/pypa/pip/issues/8454>`_)
- Headers provided by wheels in .data directories are now correctly installed
into the user-provided locations, such as ``--prefix``, instead of the virtual
environment pip is running in. (`8521 <https://github.com/pypa/pip/issues/8521>`_)

Vendored Libraries
------------------

- Vendored htmlib5 no longer imports deprecated xml.etree.cElementTree on Python 3.
- Upgrade appdirs to 1.4.4
- Upgrade certifi to 2020.6.20
- Upgrade distlib to 0.3.1
- Upgrade html5lib to 1.1
- Upgrade idna to 2.10
- Upgrade packaging to 20.4
- Upgrade requests to 2.24.0
- Upgrade six to 1.15.0
- Upgrade toml to 0.10.1
- Upgrade urllib3 to 1.25.9

Improved Documentation
----------------------

- Add ``--no-input`` option to pip docs (`7688 <https://github.com/pypa/pip/issues/7688>`_)
- List of options supported in requirements file are extracted from source of truth,
instead of being maintained manually. (`7908 <https://github.com/pypa/pip/issues/7908>`_)
- Fix pip config docstring so that the subcommands render correctly in the docs (`8072 <https://github.com/pypa/pip/issues/8072>`_)
- replace links to the old pypa-dev mailing list with https://mail.python.org/mailman3/lists/distutils-sig.python.org/ (`8353 <https://github.com/pypa/pip/issues/8353>`_)
- Fix example for defining multiple values for options which support them (`8373 <https://github.com/pypa/pip/issues/8373>`_)
- Add documentation for the ResolutionImpossible error that helps the user fix dependency conflicts (`8459 <https://github.com/pypa/pip/issues/8459>`_)
- Add feature flags to docs (`8512 <https://github.com/pypa/pip/issues/8512>`_)
- Document how to install package extras from git branch and source distributions. (`8576 <https://github.com/pypa/pip/issues/8576>`_)

20.3b1

===================

Deprecations and Removals
-------------------------

- ``pip freeze`` will stop filtering the ``pip``, ``setuptools``, ``distribute`` and ``wheel`` packages from ``pip freeze`` output in a future version.
To keep the previous behavior, users should use the new ``--exclude`` option. (`4256 <https://github.com/pypa/pip/issues/4256>`_)
- Deprecate support for Python 3.5 (`8181 <https://github.com/pypa/pip/issues/8181>`_)
- Document that certain removals can be fast tracked. (`8417 <https://github.com/pypa/pip/issues/8417>`_)
- Document that Python versions are generally supported until PyPI usage falls below 5%. (`8927 <https://github.com/pypa/pip/issues/8927>`_)
- Deprecate ``--find-links`` option in ``pip freeze`` (`9069 <https://github.com/pypa/pip/issues/9069>`_)

Features
--------

- Add ``--exclude`` option to ``pip freeze`` and ``pip list`` commands to explicitly exclude packages from the output. (`4256 <https://github.com/pypa/pip/issues/4256>`_)
- Allow multiple values for --abi and --platform. (`6121 <https://github.com/pypa/pip/issues/6121>`_)
- Add option ``--format`` to subcommand ``list`` of ``pip  cache``, with ``abspath`` choice to output the full path of a wheel file. (`8355 <https://github.com/pypa/pip/issues/8355>`_)
- Improve error message friendliness when an environment has packages with
corrupted metadata. (`8676 <https://github.com/pypa/pip/issues/8676>`_)
- Make the ``setup.py install`` deprecation warning less noisy. We warn only
when ``setup.py install`` succeeded and ``setup.py bdist_wheel`` failed, as
situations where both fails are most probably irrelevant to this deprecation. (`8752 <https://github.com/pypa/pip/issues/8752>`_)
- Check the download directory for existing wheels to possibly avoid
fetching metadata when the ``fast-deps`` feature is used with
``pip wheel`` and ``pip download``. (`8804 <https://github.com/pypa/pip/issues/8804>`_)
- When installing a git URL that refers to a commit that is not available locally
after git clone, attempt to fetch it from the remote. (`8815 <https://github.com/pypa/pip/issues/8815>`_)
- Include http subdirectory in ``pip cache info`` and ``pip cache purge`` commands. (`8892 <https://github.com/pypa/pip/issues/8892>`_)
- Cache package listings on index packages so they are guarenteed to stay stable
during a pip command session. This also improves performance when a index page
is accessed multiple times during the command session. (`8905 <https://github.com/pypa/pip/issues/8905>`_)
- New resolver: Tweak resolution logic to improve user experience when
user-supplied requirements conflict. (`8924 <https://github.com/pypa/pip/issues/8924>`_)
- Support Python 3.9. (`8971 <https://github.com/pypa/pip/issues/8971>`_)
- Log an informational message when backtracking takes multiple rounds on a specific package. (`8975 <https://github.com/pypa/pip/issues/8975>`_)
- Switch to the new dependency resolver by default. (`9019 <https://github.com/pypa/pip/issues/9019>`_)
- Remove the ``--build-dir`` option, as per the deprecation. (`9049 <https://github.com/pypa/pip/issues/9049>`_)

Bug Fixes
---------

- Propagate ``--extra-index-url`` from requirements file properly to session auth,
so that keyring auth will work as expected. (`8103 <https://github.com/pypa/pip/issues/8103>`_)
- Allow specifying verbosity and quiet level via configuration files
and environment variables. Previously these options were treated as
boolean values when read from there while through CLI the level can be
specified. (`8578 <https://github.com/pypa/pip/issues/8578>`_)
- Only converts Windows path to unicode on Python 2 to avoid regressions when a
POSIX environment does not configure the file system encoding correctly. (`8658 <https://github.com/pypa/pip/issues/8658>`_)
- List downloaded distributions before exiting ``pip download``
when using the new resolver to make the behavior the same as
that on the legacy resolver. (`8696 <https://github.com/pypa/pip/issues/8696>`_)
- New resolver: Pick up hash declarations in constraints files and use them to
filter available distributions. (`8792 <https://github.com/pypa/pip/issues/8792>`_)
- Avoid polluting the destination directory by resolution artifacts
when the new resolver is used for ``pip download`` or ``pip wheel``. (`8827 <https://github.com/pypa/pip/issues/8827>`_)
- New resolver: If a package appears multiple times in user specification with
different ``--hash`` options, only hashes that present in all specifications
should be allowed. (`8839 <https://github.com/pypa/pip/issues/8839>`_)
- Tweak the output during dependency resolution in the new resolver. (`8861 <https://github.com/pypa/pip/issues/8861>`_)
- Correctly search for installed distributions in new resolver logic in order
to not miss packages (virtualenv packages from system-wide-packages for example) (`8963 <https://github.com/pypa/pip/issues/8963>`_)
- Do not fail in pip freeze when encountering a ``direct_url.json`` metadata file
with editable=True. Render it as a non-editable ``file://`` URL until modern
editable installs are standardized and supported. (`8996 <https://github.com/pypa/pip/issues/8996>`_)

Vendored Libraries
------------------

- Fix devendoring instructions to explicitly state that ``vendor.txt`` should not be removed.
It is mandatory for ``pip debug`` command.

Improved Documentation
----------------------

- Add documentation for '.netrc' support. (`7231 <https://github.com/pypa/pip/issues/7231>`_)
- Add OS tabs for OS-specific commands. (`7311 <https://github.com/pypa/pip/issues/7311>`_)
- Add note and example on keyring support for index basic-auth (`8636 <https://github.com/pypa/pip/issues/8636>`_)
- Added initial UX feedback widgets to docs. (`8783 <https://github.com/pypa/pip/issues/8783>`_, `8848 <https://github.com/pypa/pip/issues/8848>`_)
- Add ux documentation (`8807 <https://github.com/pypa/pip/issues/8807>`_)
- Update user docs to reflect new resolver as default in 20.3. (`9044 <https://github.com/pypa/pip/issues/9044>`_)
- Improve migration guide to reflect changes in new resolver behavior. (`9056 <https://github.com/pypa/pip/issues/9056>`_)

20.2.4

===================

Deprecations and Removals
-------------------------

- Document that certain removals can be fast tracked. (`8417 <https://github.com/pypa/pip/issues/8417>`_)
- Document that Python versions are generally supported until PyPI usage falls below 5%. (`8927 <https://github.com/pypa/pip/issues/8927>`_)

Features
--------

- New resolver: Avoid accessing indexes when the installed candidate is preferred
and considered good enough. (`8023 <https://github.com/pypa/pip/issues/8023>`_)
- Improve error message friendliness when an environment has packages with
corrupted metadata. (`8676 <https://github.com/pypa/pip/issues/8676>`_)
- Cache package listings on index packages so they are guarenteed to stay stable
during a pip command session. This also improves performance when a index page
is accessed multiple times during the command session. (`8905 <https://github.com/pypa/pip/issues/8905>`_)
- New resolver: Tweak resolution logic to improve user experience when
user-supplied requirements conflict. (`8924 <https://github.com/pypa/pip/issues/8924>`_)

Bug Fixes
---------

- New resolver: Correctly respect ``Requires-Python`` metadata to reject
incompatible packages in ``--no-deps`` mode. (`8758 <https://github.com/pypa/pip/issues/8758>`_)
- New resolver: Pick up hash declarations in constraints files and use them to
filter available distributions. (`8792 <https://github.com/pypa/pip/issues/8792>`_)
- New resolver: If a package appears multiple times in user specification with
different ``--hash`` options, only hashes that present in all specifications
should be allowed. (`8839 <https://github.com/pypa/pip/issues/8839>`_)

Improved Documentation
----------------------

- Add ux documentation (`8807 <https://github.com/pypa/pip/issues/8807>`_)

20.2.3

===================

Deprecations and Removals
-------------------------

- Deprecate support for Python 3.5 (`8181 <https://github.com/pypa/pip/issues/8181>`_)

Features
--------

- Make the ``setup.py install`` deprecation warning less noisy. We warn only
when ``setup.py install`` succeeded and ``setup.py bdist_wheel`` failed, as
situations where both fails are most probably irrelevant to this deprecation. (`8752 <https://github.com/pypa/pip/issues/8752>`_)

20.2.2

===================

Bug Fixes
---------

- Only attempt to use the keyring once and if it fails, don't try again.
This prevents spamming users with several keyring unlock prompts when they
cannot unlock or don't want to do so. (`8090 <https://github.com/pypa/pip/issues/8090>`_)
- Fix regression that distributions in system site-packages are not correctly
found when a virtual environment is configured with ``system-site-packages``
on. (`8695 <https://github.com/pypa/pip/issues/8695>`_)
- Disable caching for range requests, which causes corrupted wheels
when pip tries to obtain metadata using the feature ``fast-deps``. (`8701 <https://github.com/pypa/pip/issues/8701>`_, `8716 <https://github.com/pypa/pip/issues/8716>`_)
- Always use UTF-8 to read ``pyvenv.cfg`` to match the built-in ``venv``. (`8717 <https://github.com/pypa/pip/issues/8717>`_)
- 2020 Resolver: Correctly handle marker evaluation in constraints and exclude
them if their markers do not match the current environment. (`8724 <https://github.com/pypa/pip/issues/8724>`_)

20.2.1

===================

Features
--------

- Ignore require-virtualenv in ``pip list`` (`8603 <https://github.com/pypa/pip/issues/8603>`_)

Bug Fixes
---------

- Correctly find already-installed distributions with dot (``.``) in the name
and uninstall them when needed. (`8645 <https://github.com/pypa/pip/issues/8645>`_)
- Trace a better error message on installation failure due to invalid ``.data``
files in wheels. (`8654 <https://github.com/pypa/pip/issues/8654>`_)
- Fix SVN version detection for alternative SVN distributions. (`8665 <https://github.com/pypa/pip/issues/8665>`_)
- New resolver: Correctly include the base package when specified with extras
in ``--no-deps`` mode. (`8677 <https://github.com/pypa/pip/issues/8677>`_)
- Use UTF-8 to handle ZIP archive entries on Python 2 according to PEP 427, so
non-ASCII paths can be resolved as expected. (`8684 <https://github.com/pypa/pip/issues/8684>`_)

Improved Documentation
----------------------

- Add details on old resolver deprecation and removal to migration documentation. (`8371 <https://github.com/pypa/pip/issues/8371>`_)
- Fix feature flag name in docs. (`8660 <https://github.com/pypa/pip/issues/8660>`_)

20.2

=================

Deprecations and Removals
-------------------------

- Deprecate setup.py-based builds that do not generate an ``.egg-info`` directory. (`6998 <https://github.com/pypa/pip/issues/6998>`_, `8617 <https://github.com/pypa/pip/issues/8617>`_)
- Disallow passing install-location-related arguments in ``--install-options``. (`7309 <https://github.com/pypa/pip/issues/7309>`_)
- Add deprecation warning for invalid requirements format "base>=1.0[extra]" (`8288 <https://github.com/pypa/pip/issues/8288>`_)
- Deprecate legacy setup.py install when building a wheel failed for source
distributions without pyproject.toml (`8368 <https://github.com/pypa/pip/issues/8368>`_)
- Deprecate -b/--build/--build-dir/--build-directory. Its current behaviour is confusing
and breaks in case different versions of the same distribution need to be built during
the resolution process. Using the TMPDIR/TEMP/TMP environment variable, possibly
combined with --no-clean covers known use cases. (`8372 <https://github.com/pypa/pip/issues/8372>`_)
- Remove undocumented and deprecated option ``--always-unzip`` (`8408 <https://github.com/pypa/pip/issues/8408>`_)

Features
--------

- Log debugging information about pip, in ``pip install --verbose``. (`3166 <https://github.com/pypa/pip/issues/3166>`_)
- Refine error messages to avoid showing Python tracebacks when an HTTP error occurs. (`5380 <https://github.com/pypa/pip/issues/5380>`_)
- Install wheel files directly instead of extracting them to a temp directory. (`6030 <https://github.com/pypa/pip/issues/6030>`_)
- Add a beta version of pip's next-generation dependency resolver.

Move pip's new resolver into beta, remove the
``--unstable-feature=resolver`` flag, and enable the
``--use-feature=2020-resolver`` flag. The new resolver is
significantly stricter and more consistent when it receives
incompatible instructions, and reduces support for certain kinds of
:ref:`Constraints Files`, so some workarounds and workflows may
break. More details about how to test and migrate, and how to report
issues, at :ref:`Resolver changes 2020` . Maintainers are preparing to

20.2b1

===================

Bug Fixes
---------

- Correctly treat wheels containing non-ASCII file contents so they can be
installed on Windows. (`5712 <https://github.com/pypa/pip/issues/5712>`_)
- Prompt the user for password if the keyring backend doesn't return one (`7998 <https://github.com/pypa/pip/issues/7998>`_)

Improved Documentation
----------------------

- Add GitHub issue template for reporting when the dependency resolver fails (`8207 <https://github.com/pypa/pip/issues/8207>`_)

20.1.1

===================

Deprecations and Removals
-------------------------

- Revert building of local directories in place, restoring the pre-20.1
behaviour of copying to a temporary directory. (`7555 <https://github.com/pypa/pip/issues/7555>`_)
- Drop parallelization from ``pip list --outdated``. (`8167 <https://github.com/pypa/pip/issues/8167>`_)

Bug Fixes
---------

- Fix metadata permission issues when umask has the executable bit set. (`8164 <https://github.com/pypa/pip/issues/8164>`_)
- Avoid unnecessary message about the wheel package not being installed
when a wheel would not have been built. Additionally, clarify the message. (`8178 <https://github.com/pypa/pip/issues/8178>`_)

20.1

=================

Process
-------

- Document that pip 21.0 will drop support for Python 2.7.

Features
--------

- Add ``pip cache dir`` to show the cache directory. (`7350 <https://github.com/pypa/pip/issues/7350>`_)

Bug Fixes
---------

- Abort pip cache commands early when cache is disabled. (`8124 <https://github.com/pypa/pip/issues/8124>`_)
- Correctly set permissions on metadata files during wheel installation,
to permit non-privileged users to read from system site-packages. (`8139 <https://github.com/pypa/pip/issues/8139>`_)

20.1b1

===================

Deprecations and Removals
-------------------------

- Remove emails from AUTHORS.txt to prevent usage for spamming, and only populate names in AUTHORS.txt at time of release (`5979 <https://github.com/pypa/pip/issues/5979>`_)
- Remove deprecated ``--skip-requirements-regex`` option. (`7297 <https://github.com/pypa/pip/issues/7297>`_)
- Building of local directories is now done in place, instead of a temporary
location containing a copy of the directory tree. (`7555 <https://github.com/pypa/pip/issues/7555>`_)
- Remove unused ``tests/scripts/test_all_pip.py`` test script and the ``tests/scripts`` folder. (`7680 <https://github.com/pypa/pip/issues/7680>`_)

Features
--------

- pip now implements PEP 610, so ``pip freeze`` has better fidelity
in presence of distributions installed from Direct URL requirements. (`609 <https://github.com/pypa/pip/issues/609>`_)
- Add ``pip cache`` command for inspecting/managing pip's wheel cache. (`6391 <https://github.com/pypa/pip/issues/6391>`_)
- Raise error if ``--user`` and ``--target`` are used together in ``pip install`` (`7249 <https://github.com/pypa/pip/issues/7249>`_)
- Significantly improve performance when ``--find-links`` points to a very large HTML page. (`7729 <https://github.com/pypa/pip/issues/7729>`_)
- Indicate when wheel building is skipped, due to lack of the ``wheel`` package. (`7768 <https://github.com/pypa/pip/issues/7768>`_)
- Change default behaviour to always cache responses from trusted-host source. (`7847 <https://github.com/pypa/pip/issues/7847>`_)
- An alpha version of a new resolver is available via ``--unstable-feature=resolver``. (`988 <https://github.com/pypa/pip/issues/988>`_)

Bug Fixes
---------

- Correctly freeze a VCS editable package when it is nested inside another VCS repository. (`3988 <https://github.com/pypa/pip/issues/3988>`_)
- Correctly handle ``%2F`` in URL parameters to avoid accidentally unescape them
into ``/``. (`6446 <https://github.com/pypa/pip/issues/6446>`_)
- Reject VCS URLs with an empty revision. (`7402 <https://github.com/pypa/pip/issues/7402>`_)
- Warn when an invalid URL is passed with ``--index-url`` (`7430 <https://github.com/pypa/pip/issues/7430>`_)
- Use better mechanism for handling temporary files, when recording metadata
about installed files (RECORD) and the installer (INSTALLER). (`7699 <https://github.com/pypa/pip/issues/7699>`_)
- Correctly detect global site-packages availability of virtual environments
created by PyPA’s virtualenv>=20.0. (`7718 <https://github.com/pypa/pip/issues/7718>`_)
- Remove current directory from ``sys.path`` when invoked as ``python -m pip <command>`` (`7731 <https://github.com/pypa/pip/issues/7731>`_)
- Stop failing uninstallation, when trying to remove non-existent files. (`7856 <https://github.com/pypa/pip/issues/7856>`_)
- Prevent an infinite recursion with ``pip wheel`` when ``$TMPDIR`` is within the source directory. (`7872 <https://github.com/pypa/pip/issues/7872>`_)
- Significantly speedup ``pip list --outdated`` by parallelizing index interaction. (`7962 <https://github.com/pypa/pip/issues/7962>`_)
- Improve Windows compatibility when detecting writability in folder. (`8013 <https://github.com/pypa/pip/issues/8013>`_)

Vendored Libraries
------------------

- Update semi-supported debundling script to reflect that appdirs is vendored.
- Add ResolveLib as a vendored dependency.
- Upgrade certifi to 2020.04.05.1
- Upgrade contextlib2 to 0.6.0.post1
- Upgrade distro to 1.5.0.
- Upgrade idna to 2.9.
- Upgrade msgpack to 1.0.0.
- Upgrade packaging to 20.3.
- Upgrade pep517 to 0.8.2.
- Upgrade pyparsing to 2.4.7.
- Remove pytoml as a vendored dependency.
- Upgrade requests to 2.23.0.
- Add toml as a vendored dependency.
- Upgrade urllib3 to 1.25.8.

Improved Documentation
----------------------

- Emphasize that VCS URLs using git, git+git and git+http are insecure due to
lack of authentication and encryption (`1983 <https://github.com/pypa/pip/issues/1983>`_)
- Clarify the usage of --no-binary command. (`3191 <https://github.com/pypa/pip/issues/3191>`_)
- Clarify the usage of freeze command in the example of Using pip in your program (`7008 <https://github.com/pypa/pip/issues/7008>`_)
- Add a "Copyright" page. (`7767 <https://github.com/pypa/pip/issues/7767>`_)
- Added example of defining multiple values for options which support them (`7803 <https://github.com/pypa/pip/issues/7803>`_)

Links

• PyPI: https://pypi.org/project/pip
• Changelog: https://pyup.io/changelogs/pip/
• Homepage: https://pip.pypa.io/

[coveralls]

Coverage remained the same at 42.065% when pulling 5fcda9d on pyup-update-pip-20.0.2-to-20.3 into 10a4d82 on master.

[pyup-bot]

Closing this in favor of #506