[docs] [issue29134] contextlib doc bug

[SilentGhost]

Changes by SilentGhost <ghost.adh at runbox.com>:


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assignee:  -> docs at python
components: +Documentation
nosy: +docs at python
stage:  -> patch review
type:  -> behavior
versions: +Python 3.5, Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29134>
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