[issue21589] Use better idiom in unittest example

[Ezio Melotti]

Ezio Melotti added the comment:

This is a duplicate of #11468.

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nosy: +ezio.melotti, rhettinger
resolution:  -> duplicate
stage:  -> resolved
status: open -> closed
superseder:  -> Improve unittest basic example in the doc

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21589>
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