Merge pull request #2848 from cclauss/patch-15

Transformer:  from six.moves import xrange for Python 3

research/transformer/spatial_transformer.py

@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
+
+from six.moves import xrange
 import tensorflow as tf