Support python 3.14

[danielhollas]

The crucial thing to resolve for Python 3.14 is the asyncio.get_event_loop behaviour change -- it now raises RuntimeError if there's not event loop running. See #283.

This is based on #308 that I rebased on master.

I'll try to make a minimal set of changes required for tests to pass on Python 3.14.

[codecov]

Codecov Report

❌ Patch coverage is 82.50000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.70%. Comparing base (051b3fe) to head (06d6f3c).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/plumpy/futures.py	33.34%	4 Missing ⚠️
src/plumpy/events.py	83.34%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #329      +/-   ##
==========================================
- Coverage   90.83%   90.70%   -0.13%     
==========================================
  Files          22       22              
  Lines        3009     3031      +22     
==========================================
+ Hits         2733     2749      +16     
- Misses        276      282       +6     

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[danielhollas]

The remaining errors likely come from nest_asyncio since I am seeing a similar test failure in its test suite, see danielhollas/nest_asyncio#3

 File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/nest_asyncio.py", line 29, in run
    return loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/nest_asyncio.py", line 89, in run_until_complete
    return f.result()
           ~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/asyncio/futures.py", line 208, in result
    raise self._exception.with_traceback(self._exception_tb)
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/asyncio/tasks.py", line 289, in __step_run_and_handle_result
    result = coro.send(None)
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/asyncio/tasks.py", line 487, in wait_for
    async with timeouts.timeout(timeout):
               ~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/asyncio/timeouts.py", line 88, in __aenter__
    raise RuntimeError("Timeout should be used inside a task")
RuntimeError: Timeout should be used inside a task

EDIT: I've confirmed that this is indeed the case; when I disable nest_asyncio, the failing tests are passing. (of course different tests start to fail in that case, as expected)

[danielhollas]

@unkcpz I got Python 3.14 working here 🎉
This just requires a simple patch to nest_async, see danielhollas/nest_asyncio#3

[danielhollas]

TODO: For me, report bug to uv about installing for git branches for repos with dynamic versions.

astral-sh/uv#7866

[danielhollas]

I've opened a corresponding aiida-core PR to prove that things here works:
aiidateam/aiida-core#7074

It also seems like my fix nest_asyncio works. I think the easiest way forward here (in the short term) is to vendor nest_asyncio, it is just a single file.

I think this is ready for initial review. @unkcpz