def METHOD_NAME(self) -> None:
    """
    If the DNS lookup returns an error, it will bubble up.
    """
    d = defer.ensureDeferred(self.cl.get_json("http://testserv2:8008/foo/bar"))
    self.pump()
    f = self.failureResultOf(d)
    self.assertIsInstance(f.value, DNSLookupError)