Support Python 3.14

[srittau]

No description provided.

[srittau]

In theory, python-3.14.0-beta.1 is available: https://github.com/actions/python-versions/releases. These might be some caching related issues.

Edit: The manifest hasn't been updated yet: https://github.com/actions/python-versions/blob/main/versions-manifest.json

actions/python-versions#340

[AlexWaygood]

These might be some caching related issues.

We disable the setup-python cache by using the check-latest: true setting in our workflows. So it should be available as soon as the manifest is updated in the python-versions repo

[JelleZijlstra]

This is pretty promising, just need to deal with some new type checker errors.

[srittau]

The only remaining blocker seems to be python/mypy#19020. If a mypy release is planned in the next few days, I think we can wait, otherwise I'd add a step to CI to install mypy from git.

[JelleZijlstra]

Doesn't seem like a release is imminent, probably we should just use mypy main for now

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉