p4p cython issue

[rosesyrett]

Running pytest with python 3.8 fails, both locally and in CI. Pytest fails to collect all tests, all of them having identical error messages. Here is an example of such a message:

__________________ ERROR collecting tests/panda/test_panda.py __________________
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/runner.py", line 341, in from_call
    result: Optional[TResult] = func()
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/runner.py", line 372, in <lambda>
    call = CallInfo.from_call(lambda: list(collector.collect()), "collect")
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/python.py", line 531, in collect
    self._inject_setup_module_fixture()
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/python.py", line 545, in _inject_setup_module_fixture
    self.obj, ("setUpModule", "setup_module")
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/python.py", line 310, in obj
    self._obj = obj = self._getobj()
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/python.py", line 528, in _getobj
    return self._importtestmodule()
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/python.py", line 617, in _importtestmodule
    mod = import_path(self.path, mode=importmode, root=self.config.rootpath)
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/pathlib.py", line 567, in import_path
    importlib.import_module(module_name)
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/_pytest/assertion/rewrite.py", line 178, in exec_module
    exec(co, module.__dict__)
  File "/home/runner/work/ophyd-async/ophyd-async/tests/panda/test_panda.py", line 9, in <module>
    from ophyd_async.panda import PandA, PVIEntry, SeqTable, SeqTrigger, pvi
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/ophyd_async/panda/__init__.py", line 1, in <module>
    from .panda import (
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/ophyd_async/panda/panda.py", line 23, in <module>
    from p4p.client.thread import Context
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/p4p/__init__.py", line 14, in <module>
    from .wrapper import Value, Type
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/p4p/wrapper.py", line 5, in <module>
    from . import _p4p
  File "src/p4p/_p4p.pyx", line 605, in init p4p._p4p
AttributeError: type object 'p4p._p4p.ClientProvider' has no attribute '__reduce_cython__'

[coretl]

This may be epics-base/p4p#102.

For reference it has numpy==1.24.4 and p4p==4.1.10

[rosesyrett]

could this be related to: python/cpython#84787 ?

[callumforrester]

Fixed by dropping Python3.8 support