[issue16011] "in" should be consistent with return value of __contains__

[Berker Peksag]

Changes by Berker Peksag <berker.peksag at gmail.com>:


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nosy: +berker.peksag
stage: needs patch -> patch review
versions: +Python 3.5, Python 3.6, Python 3.7 -Python 3.2, Python 3.3, Python 3.4

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue16011>
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