[issue33468] Add try-finally contextlib.contextmanager example

[Tal Einat]

Tal Einat <taleinat at gmail.com> added the comment:

A possible concrete example: Capturing sys.stdout and/or sys.stderr for testing, as in test.support.captured_output.

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nosy: +taleinat

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33468>
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