On experimental free-threaded CPython build, import whenever fails

[ariebovenberg]

Not urgent to fix, but importing on free-threaded build fails:

Python 3.13.0rc1 experimental free-threading build (main, Aug  7 2024, 15:09:54) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import whenever
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    import whenever
  File "/Users/arie/code/whenever/pysrc/whenever/__init__.py", line 2, in <module>
    from ._whenever import *
SystemError: init function of _whenever returned uninitialized object
>>>

[ariebovenberg]

After some experimentation, I can't find the cause yet. Even after removing the entire module contents, I still get the error. I'll have to do more digging.