'Assert that a status code lies inside the 2xx range.
:param response: :py:class:`httplib.HTTPResponse` to be
verified to have a status code between 200 and 299.
example::
self.assertResponseSuccessful(response)'

def assertResponseSuccessful(self, response):

    self.assertTrue((200 <= response.status_code <= 299), ('Status    code    %d    is    outside    of    the    expected    range    (2xx)\n\n%s' % (response.status, response.body)))
