Add a utility method to trial to check the type of an object

[therve]

We need something like assertIsInstance/failIfIsInstance: assert_(isinstance()) is a pain to debug because it doesn't provide any useful output.

[therve]

(In [20818]) Basic implementation.

Refs #2749.

[therve]

Ready to review in assertisinstance-2749. It's very straightforward and simple.

[therve]

Just to show the interest of the feature:

$ grep 'self.\(fail\|assert\).*isinstance' twisted/ -rsi | grep -v '.svn' | wc -l
119

[jml]

Looks great! Sorry for the delay in reviewing -- I'm a bum.

Unless things have changed without an appropriately titled notice to the mailing list, we don't indent the second line of a docstring as you've done in the new assert methods. Please dedent the second line of the docstring in failUnlessIsInstance and failIfIsInstance before landing.

You're right, this feature is woefully overdue. Thanks for doing it.

[therve]

(In [21056])

• docstring cleanup

Refs #2749

[therve]

I don't know why I did that :). Up for review again.

[jml]

No need for another review, it's just a whitespace change.

[jml]

i.e. please merge this now.

[therve]

(In [21068]) Merge assertisinstance-2749

Author: therve Reviewer: jml Fixes #2749

Add a method assertIsInstance on unittest.TestCase for checking the type of an object.