def test_copyToMissingSource(self):
        """
        If the source path is missing, L{FilePath.copyTo} raises L{OSError}.
        """
        path = filepath.FilePath(self.mktemp())
        exc = self.assertRaises(OSError, path.copyTo, b'some other path')
        self.assertEqual(exc.errno, errno.ENOENT)

        If the source path is missing, L{FilePath.copyTo} raises L{OSError}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_paths.py