def test_subunitNotInstalled(self):
        stream = NativeStringIO()
        self.patch(reporter, 'TestProtocolClient', None)
        e = self.assertRaises(Exception, reporter.SubunitReporter, stream)
        self.assertEqual("Subunit not available", str(e))
If subunit is not installed, TestProtocolClient will be None, and
dataset/ETHPy150Open twisted/twisted/twisted/trial/test/test_reporter.py/SubunitReporterNotInstalledTests.test_subunitNotInstalled