[issue30347] itertools.groupby() can fail a C assert()

[Serhiy Storchaka]

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


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assignee:  -> rhettinger
components: +Extension Modules -Interpreter Core
nosy: +rhettinger, serhiy.storchaka
stage:  -> needs patch
versions: +Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30347>
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