Add Python 3.12 support

[pquentin]

What do these changes do?

Add Python 3.12 support, as requested in #7229 and following aio-libs/frozenlist#436 as recommended by @webknjaz.

I don't think this will work because frozenlist needs to be released and updated, but that's a start.

Are there changes in behavior for the user?

No.

Related issue number

Closes #7229

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt (not needed, this only changes the CI)
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[pquentin]

I've tried installing frozenlist from git for testing purposes but it does not work as cython is not called on pip install. I'm afraid we really need a release.

[Dreamsorcerer]

Note that we won't publish wheels etc. for 3.12 until start of August at the earliest. The build system only builds wheels for stable releases (release candidate or later), due to potential ABI compatible changes (i.e. A release today might not work on the next beta release of 3.12).

This PR just ensures we are testing against 3.12.

[Dreamsorcerer]

The CI is not even starting any tests. Maybe this is not a valid pyver value? Probably better to use a similar range to what we had before.

[frenck]

This has recently changes in the setup-python action, we can now use the normal version indicator.

Suggested change

	pyver: "3.12-dev"
	pyver: "3.12"

[frenck]

Needs addition change / addition of allow-prereleases: true:

    - name: Setup Python ${{ matrix.pyver }}
      id: python-install
      uses: actions/setup-python@v4
      with:
        python-version: ${{ matrix.pyver }}
        allow-prereleases: true

[frenck]

This has recently changes in the setup-python action, we can now use the normal version indicator.

Suggested change

	pyver: "3.12-dev"
	pyver: "3.12"

[frenck]

Suggested change

	pyver: "3.12-dev"
	pyver: "3.12"

[frenck]

Suggested change

	pyver: "3.12-dev"
	pyver: "3.12"

[frenck]

Suggested change

	Use cython 3.0.0b2, fixing Python 3.12 compatibility.
	Use cython 3.0.0, fixing Python 3.12 compatibility.

[frenck]

This one is now stable: https://github.com/cython/cython/releases/tag/3.0.0

Suggested change

	cython==3.0.0b3
	cython==3.0.0

[pquentin]

Thanks for the review. However this was more a proof of concept and I have a lost interest since then. Feel free to reuse my pull request, it has the same license as the code itself.

Also thanks for the 3.12 tip, I shared it on Mastodon where it was well received: https://fosstodon.org/@quentinpradet/110748145154814131

[Dreamsorcerer]

I've updated and merged tests for 3.12. There are still a few issues to get it working though. If anybody would like to help getting the tests passing for 3.12, then we'll be able to include support in the next release.