def test_renameNotExisting(self):
        """
        Renaming a directory that doesn't exist should fail with
        L{ftp.FileNotFoundError}.
        """
        d = self.shell.rename(('foo',), ('bar',))
        return self.assertFailure(d, ftp.FileNotFoundError)

        Renaming a directory that doesn't exist should fail with
        L{ftp.FileNotFoundError}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_ftp.py