Remove __future__ imports.

tests/test_tokenization_roberta.py

@@ -12,7 +12,7 @@
 # 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, division, print_function, unicode_literals
+
 
 import json
 import os