def test_notFile(self):
        """
        L{runner.filenameToModule} raises a C{ValueError} when a non-existing
        file is passed.
        """
        err = self.assertRaises(ValueError, runner.filenameToModule, 'it')
        self.assertEqual(str(err), "'it' doesn't exist")

        L{runner.filenameToModule} raises a C{ValueError} when a non-existing
        file is passed.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_loader.py