[issue36097] Use only public C-API in _xxsubinterpreters module.

[Eric Snow]

Eric Snow <ericsnowcurrently at gmail.com> added the comment:

Actually, this is independent of that change.  It had to be reverted because the PR was based on the earlier PR from #33608.  So I may merge this separately...or not, since it would mean having to sort out merge conflicts. :)

----------
stage:  -> needs patch

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue36097>
_______________________________________