+1 for Benjamin's patch, having just been bitten by this exact problem.

I'm trying to do unit testing, checking both that a piece of code produces a DeprecationWarning and that it gives the correct result, with something like:

    with warnings.catch_warnings():
        warnings.filterwarnings("ignore", category=DeprecationWarning)
        self.assertEqual(my_func(my_args), expected_result)

    with warnings.catch_warnings():
        warnings.filterwarnings("error", category=DeprecationWarning)
        self.assertRaises(DeprecationWarning, my_func, *my_args)

The first call still registers the warning, even though it's ignored, so the second assertRaises fails.  Benjamin's patch would seem to provide a way to fix this.

Perhaps I'm missing an obvious better way to do this.

N.B. The above is a too simple version of the real problem: it actually works as intended, for fragile reasons:  the "ignore"d warning is registered on __name__, while the "always"d warning ends up being registered on unittest.case, so there's no conflict.