'Fail the test if C{first} == C{second}.
@param msg: if msg is None, then the failure message will be
\'%r == %r\' % (first, second)'

def assertNotEqual(self, first, second, msg=None):

    if (not (first != second)):
        raise self.failureException((msg or ('%r    ==    %r' % (first, second))))
    return first
