Update pip to 20.1

[pyup-bot]

This PR updates pip from 20.0.2 to 20.1.

Changelog

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/