def test_invalidSubdir(self):
        """
        Verify that a subdirectory that doesn't exist is reported as such.
        """
        sub2 = self.path.child(b'sub2')
        self.assertFalse(sub2.exists(),
                    "This directory does not exist.")

        Verify that a subdirectory that doesn't exist is reported as such.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_paths.py