GH-111784: Fix segfault by keeping pyexpat module alive for capsule lifetime

[kumaraditya303]

This fixes the segfault reported on the issue, it also avoids adding any new API as it has to be backported and is minimal.

• Issue: Segfault during deallocation of _elementtree.XMLParser #111784

[Eclips4]

With this patch I still getting segmentation fault:

./python.exe scratch.py
/Users/admin/Library/Application Support/JetBrains/CLion2023.2/scratches/scratch.py:12: DeprecationWarning: There is no current event loop
  asyncio.ensure_future(self._end_stream_wait())
zsh: segmentation fault  ./python.exe 

[erlend-aasland]

Looks good to me. @Eclips4, did you do a clean build before testing this? (git clean -fdx)

[Eclips4]

Looks good to me. @Eclips4, did you do a clean build before testing this? (git clean -fdx)

Yes.

[mgorny]

I'm seeing the same segfault too, with my original reproducer. (I've applied this change on top of 3.12.0)

[Eclips4]

I'm seeing the same segfault too, with my original reproducer. (I've applied this change on top of 3.12.0)

My week's research says that there's two possible segfaults. Soon I'll try to summarize what's actually happening.

[Eclips4]

Closing it due to merge of #113405