fix unicode in tokenization tests

tests/tokenization_test.py

@@ -12,16 +12,17 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 import os
 import unittest
 from io import open
 
-from pytorch_pretrained_bert.tokenization import (BertTokenizer, BasicTokenizer, WordpieceTokenizer,
-                                                  _is_whitespace, _is_control, _is_punctuation)
+from pytorch_pretrained_bert.tokenization import (BasicTokenizer,
+                                                  BertTokenizer,
+                                                  WordpieceTokenizer,
+                                                  _is_control, _is_punctuation,
+                                                  _is_whitespace)
 
 
 class TokenizationTest(unittest.TestCase):