def test_credentialsInvalidSignature(self):
        self.credentials.signature = (
            keys.Key.fromString(keydata.privateDSA_openssh).sign(b'foo'))
        self.failureResultOf(self.checker.requestAvatarId(self.credentials),
                             UnauthorizedLogin)
Calling L{checkers.SSHPublicKeyChecker.requestAvatarId} with
dataset/ETHPy150Open twisted/twisted/twisted/conch/test/test_checkers.py/SSHPublicKeyCheckerTests.test_credentialsInvalidSignature