Upgrade pycodestyle to avoid FutureWarning on Python 3.7

Author: haikoschol

requirements.txt

@@ -8,7 +8,7 @@ django-filter==2.1.0
 
 # Tests
 pytest==3.2.3
-pycodestyle==2.3.1
+pycodestyle==2.5.0
 
 # Deployment
 gunicorn==19.7.1