Gunicorn+Tornado is for PyPy. Py2/Py3 can use Gunicron 19.0.

config/requirements-py3.txt

@@ -8,7 +8,7 @@ ujson==1.33
 # uwsgi is released too often to stick on single version.
 uwsgi
 
-gunicorn==18.0
+gunicorn==19.0
 meinheld==0.5.6
 
 # Tornado

config/requirements.txt

@@ -9,7 +9,7 @@ gevent==1.0.1
 # uwsgi is released too often to stick on single version.
 uwsgi
 
-gunicorn==18.0
+gunicorn==19.0
 meinheld==0.5.6
 
 # Tornado