Build wheels for Python 3.10 RC1?

[hugovk]

Python 3.10.0 final is due for release in October:

• https://www.python.org/dev/peps/pep-0619/

The first release candidate is now out and the Python release team has issued a call to action for community members:

We strongly encourage maintainers of third-party Python projects to prepare their projects for 3.10 compatibilities during this phase. As always, report any issues to the Python bug tracker.

https://discuss.python.org/t/python-3-10-0rc1-is-now-available/9982?u=hugovk

It should be quite safe to release wheels for release candidate. ABI for Python 3.10 should be frozen from now on, even for bugfixes. From release notes:

There will be no ABI changes from this point forward in the 3.10 series and the goal is that there will be as few code changes as possible.

https://www.python.org/downloads/release/python-3100rc1/

What do we need to do to create wheels using the Python 3.10 release candidate?

[mattip]

• use MB_PYTHON_VERSION=3.10
• for testing, use DOCKER_TEST_IMAGE=multibuild/focal_{PLAT} (will not work with 32-bit linux. For 32-bit linux do not use any DOCKER_TEST_IMAGE directive, and consider dropping 32-bit linux wheels).
• for good measure, create only manylinux2014 wheels with MB_ML_VER=2014
  For macOS and windows, you need to use a CI service that provides the python versions. Right now it seems github actions would be your best bet.

[hugovk]

Thanks all, closing this now #422 is merged, we've updated in python-pillow/pillow-wheels#215.

[radarhere]

Fyi, #423 has updated the default MB_ML_VER from 1 to 2014.