[issue31642] None value in sys.modules no longer blocks import

[Serhiy Storchaka]

Change by Serhiy Storchaka <storchaka+cpython at gmail.com>:


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keywords: +patch
pull_requests: +3815
stage: needs patch -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31642>
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