[issue34110] cPickle may raise AttributeError when loading concurrently in threads

[Pablo Galindo Salgado]

Change by Pablo Galindo Salgado <pablogsal at gmail.com>:


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versions: +Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34110>
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