'Test that two dictionaries are equal.
Implemented here because this method was not available until Python
2.6. This asserts that the unique set of keys are the same in a and b.
Also asserts that the value of each key is the same in a and b using
the is operator.'

def assertDictEqual(self, a, b, msg=None):

    assert (set(keys(a)) == set(keys(b)))
    for key in keys(a):
        assert (a[key] == b[key])
