[enh] py3 compatibility

.travis.yml

@@ -9,6 +9,7 @@ addons:
 language: python
 python:
   - "2.7"
+  - "3.6"
 before_install:
   - "export DISPLAY=:99.0"
   - "sh -e /etc/init.d/xvfb start"
@@ -24,9 +25,9 @@ script:
   - ./manage.sh styles
   - ./manage.sh grunt_build
   - ./manage.sh tests
-  - ./manage.sh py_test_coverage
 after_success:
-  coveralls
+  - ./manage.sh py_test_coverage
+  - coveralls
 notifications:
   irc:
     channels: