tests pass on python 2 and 3

tests/tokenization_openai_test.py

@@ -17,7 +17,6 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 import os
 import unittest
 import json
-from io import open
 
 from pytorch_pretrained_bert.tokenization_openai import OpenAIGPTTokenizer
 
@@ -32,10 +31,10 @@ class OpenAIGPTTokenizationTest(unittest.TestCase):
                  "low</w>", "lowest</w>", "newer</w>", "wider</w>"]
         vocab_tokens = dict(zip(vocab, range(len(vocab))))
         merges = ["#version: 0.2", "l o", "lo w", "e r</w>", ""]
-        with open("/tmp/openai_tokenizer_vocab_test.json", "wb") as fp:
+        with open("/tmp/openai_tokenizer_vocab_test.json", "w") as fp:
             json.dump(vocab_tokens, fp)
             vocab_file = fp.name
-        with open("/tmp/openai_tokenizer_merges_test.txt", "w", encoding='utf-8') as fp:
+        with open("/tmp/openai_tokenizer_merges_test.txt", "w") as fp:
             fp.write("\n".join(merges))
             merges_file = fp.name