Create wheels for Python 3.11 beta

[hugovk]

We'll release binary wheels for the next Pillow release (9.2.0, 1st July 2022, #6366).

According to the Python 3.11 release manager:

We strongly encourage maintainers of third-party Python projects to test with 3.11 during the beta phase and report issues found to the Python bug tracker as soon as possible. While the release is planned to be feature complete entering the beta phase, it is possible that features may be modified or, in rare cases, deleted up until the start of the release candidate phase (Monday, 2021-08-02). Our goal is have no ABI changes after beta 4 [5] and as few code changes as possible after 3.11.0rc1, the first release candidate. To achieve that, it will be extremely important to get as much exposure for 3.11 as possible during the beta phase.

Please keep in mind that this is a preview release and its use is not recommended for production environments.

Therefore it's possible the ABI may change before the official release, so these 3.11 wheels can also be considered preview releases, but will help people test and prepare their projects with 3.11.

[hugovk]

What do we need to build 3.11 wheels?

Does https://github.com/multi-build/multibuild support building wheels for 3.11?

(Re: #5569 for adding support for Python 3.10, specifically python-pillow/pillow-wheels#215 and python-pillow/pillow-wheels#217).

There are 3.11 wheels at https://www.lfd.uci.edu/~gohlke/pythonlibs/#_pillow so we'll be good for Windows.

[radarhere]

The last Python beta release before July 1 will be Python 3.11 beta 4, due out today.

Once that is out, yes, a multibuild PR should be created to support building wheels for 3.11.

As for testing those wheels as part of our CI, I expect that will require a PR to https://github.com/multi-build/docker-images for 64-bit, and https://github.com/matthew-brett/trusty for 32-bit.

[hugovk]

The last Python beta release before July 1 will be Python 3.11 beta 4, due out today.

There are (currently five) release blockers:

• https://mail.python.org/archives/list/python-dev@python.org/thread/ORCYBRP432J36LXP32IDX6KLRE7Z646V/

• https://github.com/python/cpython/issues?q=is%3Aissue+is%3Aopen+label%3Arelease-blocker+label%3A3.11+

[radarhere]

Interestingly, replies on python/cpython#89480 and python/release-tools#16 say they were release blockers for beta 2... so maybe they aren't absolute "blockers".

[radarhere]

b4 might be released next week? https://mail.python.org/archives/list/python-dev@python.org/thread/7AT3YTUJOYMZI4VNMSJ42BE6ZNR7GANM/

For now though, I've created python-pillow/pillow-wheels#302 to add b3 to pillow-wheels.

[radarhere]

python-pillow/pillow-wheels#302 has been merged, so Pillow 9.2.0 can have Python 3.11.0 beta 3 wheels.

[radarhere]

Python 3.11.0 beta 3 is still the latest beta, and Pillow 9.2.0 has been released.

So this is resolved. Pillow 9.3.0 is scheduled to be released with the Python 3.11.0 final version.