[issue40364] asyncio: replace _compute_returncode() with os.waitstatus_to_exitcode()

[STINNER Victor]

Change by STINNER Victor <vstinner at python.org>:


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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed
versions: +Python 3.10 -Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40364>
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