fix: add support for Python 3.14

[Jenselme]

Description

• Add support for Python 3.14. It didn’t work previously because asyncio.get_event_loop now fails if no event loop is active. See https://docs.python.org/3.14/library/asyncio-eventloop.html#asyncio.get_event_loop and the initial bug report Support python 3.14 #193 for more details
• Add Python 3.14 to GitHub actions and tox matrix.
• Update Pytest to 8.4.0: it’s the first version to officially support Python 3.14 See https://docs.pytest.org/en/stable/changelog.html#pytest-8-4-0-2025-06-02 Previous versions won’t work because of a breaking change in Python’s AST in 3.14.

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Related Issue(s)

Closes or relates to #193

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Checklist

• I have referenced relevant issue numbers above
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that
  my feature works
• I have added necessary documentation (if appropriate)
• My code follows the style guidelines of this project

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AI Assistance Disclosure

Created the relevant file in .audit.

Review of the proposed Python 3.14 compatibility fix

Reviewed by: GitHub Copilot (on behalf of @oberstet) See #193 (comment) for the original comment.

The patch (commit) correctly addresses Python 3.14 compatibility by adding a fallback when asyncio.get_event_loop() raises a RuntimeError. If no event loop is running, it creates a new one and sets it. This pattern is now used in both the test utility code and in txaio/aio.py.

This approach is:

• Consistent with recommendations from Python’s documentation for event loop management in 3.14+.
• Minimal and targeted (affects only relevant code).
• Backwards compatible with CPython 3.10 and earlier, and also works on PyPy, since the code first tries the legacy method and only falls back if needed.

Summary:
This fix is a robust way to support Python 3.14 and maintain compatibility with older Python versions.

[Jenselme]

I have run the test locally with tox and it passes on Python 3.10, 3.12 and 3.14. I guess it’s failing on Ubuntu because until 3.14 is released, it’s 3.14-dev and not 3.14 that should be used. Should I enable with the -dev suffix or just wait for 3.14 to be released?

[oberstet]

just some comments from my side, actually, I want to move everything (txaio, autobahn-python, crossbar, ..) to uv: crossbario/autobahn-python#1665 - so this would mean latest cpython is 3.14.0b3:

oberstet@amd-ryzen5:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 24.04.2 LTS
Release:        24.04
Codename:       noble
oberstet@amd-ryzen5:~$ which uv
/home/oberstet/.local/bin/uv
oberstet@amd-ryzen5:~$ uv --version
uv 0.7.19
oberstet@amd-ryzen5:~$ uv python list
cpython-3.14.0b3-linux-x86_64-gnu                 <download available>
cpython-3.14.0b3+freethreaded-linux-x86_64-gnu    <download available>
cpython-3.13.5-linux-x86_64-gnu                   .local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/bin/python3.13
cpython-3.13.5+freethreaded-linux-x86_64-gnu      <download available>
cpython-3.12.11-linux-x86_64-gnu                  .local/share/uv/python/cpython-3.12.11-linux-x86_64-gnu/bin/python3.12
cpython-3.12.3-linux-x86_64-gnu                   /usr/bin/python3.12
cpython-3.12.3-linux-x86_64-gnu                   /usr/bin/python3 -> python3.12
cpython-3.11.13-linux-x86_64-gnu                  .local/share/uv/python/cpython-3.11.13-linux-x86_64-gnu/bin/python3.11
cpython-3.10.18-linux-x86_64-gnu                  .local/share/uv/python/cpython-3.10.18-linux-x86_64-gnu/bin/python3.10
cpython-3.9.23-linux-x86_64-gnu                   <download available>
cpython-3.8.20-linux-x86_64-gnu                   <download available>
pypy-3.11.11-linux-x86_64-gnu                     .local/share/uv/python/pypy-3.11.11-linux-x86_64-gnu/bin/pypy3.11
pypy-3.10.16-linux-x86_64-gnu                     .local/share/uv/python/pypy-3.10.16-linux-x86_64-gnu/bin/pypy3.10
pypy-3.9.19-linux-x86_64-gnu                      <download available>
pypy-3.8.16-linux-x86_64-gnu                      <download available>
graalpy-3.11.0-linux-x86_64-gnu                   <download available>
graalpy-3.10.0-linux-x86_64-gnu                   <download available>
graalpy-3.8.5-linux-x86_64-gnu                    <download available>
oberstet@amd-ryzen5:~$ 

I have migrated my private Python project/repos already, but still didn't had time yet to get to txaio etc, even though crossbario/autobahn-python#1669 already is (mostly) just/uv.

in general, ideally, I would like best not care at all what OS distro CPython or PyPy packages are there. now, this hits a wall for me since I am doing stuff with KiCad and the CPython (cpyext) API, and I don't want to deal with building that from source, want to use PTH files, which works - if I use the same uv Python version as the OS one. which is 3.12. but that's not an issue for txaio or autobahn-python ..