[issue46070] _PyImport_FixupExtensionObject() regression causing a crash in subintepreters

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

bug.py:

* Python 3.7 branch doesn't crash
* Python 3.8 branch does crash

So the regression was introduced in Python 3.8.

git bisect points me to this change:
---
commit 13915a3100608f011b29da2f3716c990f523b631 (refs/bisect/bad)
Author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
Date:   Mon Oct 7 09:38:00 2019 -0700

    bpo-36356: Fix memory leak in _asynciomodule.c (GH-16598)
    
    (cherry picked from commit 321def805abc5b7c92c7e90ca90cb2434fdab855)
    
    Co-authored-by: Ben Harper <btharper1221 at gmail.com>
---

Before this change, bug.py doesn't crash. With this change, bug.py does crash.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46070>
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