[issue31586] SystemError in _collections._count_element() in case of a bad mapping argument

[Serhiy Storchaka]

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


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nosy: +rhettinger, serhiy.storchaka
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/issue31586>
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