message: python2.7 compatibility: explicit file encoding
diff: @@ -57,7 +57,7 @@ class BasicTC(unittest.TestCase):
  # with open(ref_file, "w") as f:
  # f.write(res_str)
  - with open(ref_file) as f:
  + with open(ref_file, encoding="utf-8") as f:
  ref = f.read()
  self.assertEqual(ref, res_str)
  