build freethreading wheels

[mayeut]

Summary

• OS: all
• Bug fix: yes
• Type: wheels
• Fix Release Python 3.13t (free-threading) wheel #2476

Description

build freethreading wheels
fix tests issues discovered while adding those

[mayeut]

The macOS-14 failure is just a flaky test. Nothing to do with this PR.

[giampaolo]

Sorry for the probably noob questions, but here goes:

1. How many additional .whl files does this produce? For what platforms?
2. How many additional test runs / jobs are being executed?
3. Are additional unit tests run specifically for free-thread python? Or this just produces the .whl file without running tests?

[mayeut]

How many additional .whl files does this produce? For what platforms?

This generates 1 additional wheel per axis in the build matrix so 7 additional wheels (2 for macOS, 2 for Windows, 3 for Linux). It only needed tweaking cibuildwheel configuration in order to build & tests those wheels.

How many additional test runs / jobs are being executed?
Are additional unit tests run specifically for free-thread python? Or this just produces the .whl file without running tests?

The existing set of tests is ran for those new wheels, except on Windows where the tests are not run pending pywin32 availability for free-threading python (see the comment in pyproject.toml). There are no new specific tests.