Test on Python 3.12

[atugushev]

Contributor checklist

• Provided the tests for the changes.
• Assure PR title is short, clear, and good to be included in the user-oriented changelog

Maintainer checklist

• Assure one of these labels is present: backwards incompatible, feature, enhancement, deprecation, bug, dependency, docs or skip-changelog as they determine changelog listing.
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[webknjaz]

@atugushev instead of deadsnakes you could just use ~3.12.0-0 from GH

[atugushev]

@webknjaz I followed the pattern in ci.yaml. Isn't "deadsnakes" builds main python nightly which is why we use it?

[webknjaz]

Yes and no. Deadsnakes builds CPython's repo branch every day. It is truly unstable.
GitHub builds tagged releases, they are updated less frequently, providing less surprises every day.
Originally, deadsnakes were used because GH was slow to provide alphas and to emulate what Travis CI used to have.
So depending on the motivation, you might want to use one or the other.

[atugushev]

@webknjaz thanks for the info. I guess we can switch to GHA completely then. I'll open a PR shortly.