Log Message:
py-packaging: update to 21.2.

21.2 - 2021-10-29
~~~~~~~~~~~~~~~~~

* Update documentation entry for 21.1.

21.1 - 2021-10-29
~~~~~~~~~~~~~~~~~

* Update pin to pyparsing to exclude 3.0.0.

21.0 - 2021-07-03
~~~~~~~~~~~~~~~~~

* PEP 656: musllinux support (:issue:`411`)
* Drop support for Python 2.7, Python 3.4 and Python 3.5.
* Replace distutils usage with sysconfig (:issue:`396`)
* Add support for zip files in ``parse_sdist_filename`` (:issue:`429`)
* Use cached ``_hash`` attribute to short-circuit tag equality comparisons \ 
(:issue:`417`)
* Specify the default value for the ``specifier`` argument to ``SpecifierSet`` \ 
(:issue:`437`)
* Proper keyword-only "warn" argument in packaging.tags (:issue:`403`)
* Correctly remove prerelease suffixes from ~= check (:issue:`366`)
* Fix type hints for ``Version.post`` and ``Version.dev`` (:issue:`393`)
* Use typing alias ``UnparsedVersion`` (:issue:`398`)
* Improve type inference for ``packaging.specifiers.filter()`` (:issue:`430`)
* Tighten the return type of ``canonicalize_version()`` (:issue:`402`)