Update pip to 21.3.1

[pyup-bot]

This PR updates pip from 21.2.3 to 21.3.1.

Changelog

21.3.1

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


Bug Fixes
---------


- Always refuse installing or building projects that have no ``pyproject.toml`` nor
``setup.py``. (`10531 <https://github.com/pypa/pip/issues/10531>`_)
- Tweak running-as-root detection, to check ``os.getuid`` if it exists, on Unix-y and non-Linux/non-MacOS machines. (`10565 <https://github.com/pypa/pip/issues/10565>`_)
- When installing projects with a ``pyproject.toml`` in editable mode, and the build
backend does not support :pep:`660`, prepare metadata using
``prepare_metadata_for_build_wheel`` instead of ``setup.py egg_info``. Also, refuse
installing projects that only have a ``setup.cfg`` and no ``setup.py`` nor
``pyproject.toml``. These restore the pre-21.3 behaviour. (`10573 <https://github.com/pypa/pip/issues/10573>`_)
- Restore compatibility of where configuration files are loaded from on MacOS (back to ``Library/Application Support/pip``, instead of ``Preferences/pip``). (`10585 <https://github.com/pypa/pip/issues/10585>`_)

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


- Upgrade pep517 to 0.12.0

21.3

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

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

- Improve deprecation warning regarding the copying of source trees when installing from a local directory. (`10128 <https://github.com/pypa/pip/issues/10128>`_)
- Suppress location mismatch warnings when pip is invoked from a Python source
tree, so ``ensurepip`` does not emit warnings on CPython ``make install``. (`10270 <https://github.com/pypa/pip/issues/10270>`_)
- On Python 3.10 or later, the installation scheme backend has been changed to use
``sysconfig``. This is to anticipate the deprecation of ``distutils`` in Python
3.10, and its scheduled removal in 3.12. For compatibility considerations, pip
installations running on Python 3.9 or lower will continue to use ``distutils``. (`10358 <https://github.com/pypa/pip/issues/10358>`_)
- Remove the ``--build-dir`` option and aliases, one last time. (`10485 <https://github.com/pypa/pip/issues/10485>`_)
- In-tree builds are now the default. ``--use-feature=in-tree-build`` is now
ignored. ``--use-deprecated=out-of-tree-build`` may be used temporarily to ease
the transition. (`10495 <https://github.com/pypa/pip/issues/10495>`_)
- Un-deprecate source distribution re-installation behaviour. (`8711 <https://github.com/pypa/pip/issues/8711>`_)

Features
--------

- Replace vendored appdirs with platformdirs. (`10202 <https://github.com/pypa/pip/issues/10202>`_)
- Support `PEP 610 <https://www.python.org/dev/peps/pep-0610/>`_ to detect
editable installs in ``pip freeze`` and  ``pip list``. The ``pip list`` column output
has a new ``Editable project location`` column, and the JSON output has a new
``editable_project_location`` field. (`10249 <https://github.com/pypa/pip/issues/10249>`_)
- ``pip freeze`` will now always fallback to reporting the editable project
location when it encounters a VCS error while analyzing an editable
requirement. Before, it sometimes reported the requirement as non-editable. (`10410 <https://github.com/pypa/pip/issues/10410>`_)
- ``pip show`` now sorts ``Requires`` and ``Required-By`` alphabetically. (`10422 <https://github.com/pypa/pip/issues/10422>`_)
- Do not raise error when there are no files to remove with ``pip cache purge/remove``.
Instead log a warning and continue (to log that we removed 0 files). (`10459 <https://github.com/pypa/pip/issues/10459>`_)
- When backtracking during dependency resolution, prefer the dependencies which are involved in the most recent conflict. This can significantly reduce the amount of backtracking required. (`10479 <https://github.com/pypa/pip/issues/10479>`_)
- Cache requirement objects, to improve performance reducing reparses of requirement strings. (`10550 <https://github.com/pypa/pip/issues/10550>`_)
- Support editable installs for projects that have a ``pyproject.toml`` and use a
build backend that supports :pep:`660`. (`8212 <https://github.com/pypa/pip/issues/8212>`_)
- When a revision is specified in a Git URL, use git's partial clone feature to speed up source retrieval. (`9086 <https://github.com/pypa/pip/issues/9086>`_)
- Add a ``--debug`` flag, to enable a mode that doesn't log errors and propagates them to the top level instead. This is primarily to aid with debugging pip's crashes. (`9349 <https://github.com/pypa/pip/issues/9349>`_)
- If a host is explicitly specified as trusted by the user (via the --trusted-host option), cache HTTP responses from it in addition to HTTPS ones. (`9498 <https://github.com/pypa/pip/issues/9498>`_)

Bug Fixes
---------

- Present a better error message, when a ``file:`` URL is not found. (`10263 <https://github.com/pypa/pip/issues/10263>`_)
- Fix the auth credential cache to allow for the case in which
the index url contains the username, but the password comes
from an external source, such as keyring. (`10269 <https://github.com/pypa/pip/issues/10269>`_)
- Fix double unescape of HTML ``data-requires-python`` and ``data-yanked`` attributes. (`10378 <https://github.com/pypa/pip/issues/10378>`_)
- New resolver: Fixes depth ordering of packages during resolution, e.g. a dependency 2 levels deep will be ordered before a dependency 3 levels deep. (`10482 <https://github.com/pypa/pip/issues/10482>`_)
- Correctly indent metadata preparation messages in pip output. (`10524 <https://github.com/pypa/pip/issues/10524>`_)

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

- Remove appdirs as a vendored dependency.
- Upgrade distlib to 0.3.3
- Upgrade distro to 1.6.0
- Patch pkg_resources to use platformdirs rather than appdirs.
- Add platformdirs as a vendored dependency.
- Upgrade progress to 1.6
- Upgrade resolvelib to 0.8.0
- Upgrade urllib3 to 1.26.7

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

- Update links of setuptools as setuptools moved these documents. The Simple Repository link now points to PyPUG as that is the canonical place of packaging specification, and setuptools's ``easy_install`` is deprecated. (`10430 <https://github.com/pypa/pip/issues/10430>`_)
- Create a "Build System Interface" reference section, for documenting how pip interacts with build systems. (`10497 <https://github.com/pypa/pip/issues/10497>`_)

21.2.4

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

Bug Fixes
---------

- Fix 3.6.0 compatibility in link comparison logic. (`10280 <https://github.com/pypa/pip/issues/10280>`_)

Links

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

[pyup-bot]

Closing this in favor of #327