[issue13387] add exact_type argument to assertIsInstance

[Florent Xicluna]

Florent Xicluna <florent.xicluna at gmail.com> added the comment:

I would say that this one is clear too:
  aelf.assertTrue(isinstance(obj, cls))

except that the failure message is not very friendly:
  AssertionError: False is not true


If we keep assertIsInstance, more people will continue to misuse it just because the method exist, when they really want to check (type(obj) is cls).

An option could be to add a snippet to the documentation of `assertIsInstance` stating that the right way to check exact type is `assertIs(type(obj), cls)`.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13387>
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