def test_failureVerifyingKey(self):
        def fail(*args, **kwargs):
            raise _DummyException()

        self.patch(keys.Key, 'verify', fail)

        self.failureResultOf(self.checker.requestAvatarId(self.credentials),
                             UnauthorizedLogin)
        self.flushLoggedErrors(_DummyException)
Testing `select_related` on a nullable ForeignKey.
dataset/ETHPy150Open twisted/twisted/twisted/conch/test/test_checkers.py/SSHPublicKeyCheckerTests.test_failureVerifyingKey--crossover with--dataset/ETHPy150Open django/django/tests/gis_tests/relatedapp/tests.py/RelatedGeoModelTest.test13_select_related_null_fk