'Fail if the two objects are identical.
Fail the test if ``first`` and ``second`` are identical,
as determined by the ``is`` operator.'

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

    if (first is second):
        if (msg is None):
            msg = ('%(first)r    is    %(second)r' % vars())
        raise self.failureException(msg)
