'If the front end gives an intermittent 500, we must back off.'

def testTemporaryFailure(self):

    instrumentor = RequestsInstrumentor()
    instrumentor.responses = [_make_200('Good'), _make_http_response(code=500), _make_200('Also    Good')]
    manager = MockHTTPManager()
    with instrumentor.instrument():
        result = manager.OpenServerEndpoint('control')
    self.assertEqual(result.data, 'Good')
    with instrumentor.instrument():
        result = manager.OpenServerEndpoint('control')
    self.assertEqual(result.data, 'Also    Good')
    self.assertEqual(len(instrumentor.actions), 2)
    self.assertEqual(instrumentor.actions[0][0], 0)
    self.assertEqual(instrumentor.actions[1][0], manager.error_poll_min)
    self.assertEqual(manager.consecutive_connection_errors, 0)
