Update pip to 21.1.3

[pyup-bot]

This PR updates pip from 21.1 to 21.1.3.

Changelog

21.1.3

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

Bug Fixes
---------

- Remove unused optional ``tornado`` import in vendored ``tenacity`` to prevent old versions of Tornado from breaking pip. (`10020 <https://github.com/pypa/pip/issues/10020>`_)
- Require ``setup.cfg``-only projects to be built via PEP 517, by requiring an explicit dependency on setuptools declared in pyproject.toml. (`10031 <https://github.com/pypa/pip/issues/10031>`_)

21.1.2

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

Bug Fixes
---------

- New resolver: Correctly exclude an already installed package if its version is
known to be incompatible to stop the dependency resolution process with a clear
error message. (`9841 <https://github.com/pypa/pip/issues/9841>`_)
- Allow ZIP to archive files with timestamps earlier than 1980. (`9910 <https://github.com/pypa/pip/issues/9910>`_)
- Emit clearer error message when a project root does not contain either
``pyproject.toml``, ``setup.py`` or ``setup.cfg``. (`9944 <https://github.com/pypa/pip/issues/9944>`_)
- Fix detection of existing standalone pip instance for PEP 517 builds. (`9953 <https://github.com/pypa/pip/issues/9953>`_)

21.1.1

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

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

- Temporarily set the new "Value for ... does not match" location warnings level
to *DEBUG*, to hide them from casual users. This prepares pip 21.1 for CPython
inclusion, while pip maintainers digest the first intake of location mismatch
issues for the ``distutils``-``sysconfig`` transition. (`9912 <https://github.com/pypa/pip/issues/9912>`_)

Bug Fixes
---------

- This change fixes a bug on Python <=3.6.1 with a Typing feature added in 3.6.2 (`9831 <https://github.com/pypa/pip/issues/9831>`_)
- Fix compatibility between distutils and sysconfig when the project name is unknown outside of a virtual environment. (`9838 <https://github.com/pypa/pip/issues/9838>`_)
- Fix Python 3.6 compatibility when a PEP 517 build requirement itself needs to be
built in an isolated environment. (`9878 <https://github.com/pypa/pip/issues/9878>`_)

Links

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