Originally reported as a bug against unittest2: http://code.google.com/p/unittest-ext/issues/detail?id=3

There are some assert* methods that don't have their assertNot* 
counterparts. There's assertDictEqual, assertSequenceEqual, 
assertRegexpMatches, but no assertDictNotEqual, assertSequenceNotEqual, 
assertRegexpNotMatches, for example.

They should be present for the sake of completeness (I don't like to have to look into the docs to check if a method has a negative counterpart), but also because they ask for a custom output. For example, the error accompanying assertRegexpNotMatches could show the matching part of the text, which is the part that really interests me. assert_(re.match(...)) will only tell me that None is not true...