def test_findNonFile(self):
        """
        findByName, given a file path that doesn't exist, will raise a
        ValueError saying that it is not a Python file.
        """
        path = util.sibpath(__file__, 'nonexistent.py')
        self.assertRaises(ValueError, self.loader.findByName, path)

        findByName, given a file path that doesn't exist, will raise a
        ValueError saying that it is not a Python file.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_loader.py