add gunicorn logging

compose/django/gunicorn.sh

@@ -1,4 +1,4 @@
 #!/bin/sh
 python /app/manage.py collectstatic --noinput
 python /app/manage.py compilescss
-/usr/local/bin/gunicorn config.wsgi -w 4 -b unix:/data/sockets/gunicorn.sock --chdir=/app
+/usr/local/bin/gunicorn config.wsgi -w 4 -b unix:/data/sockets/gunicorn.sock --error-logfile /var/log/gunicorn/gunicorn-error.log --chdir=/app

stage.yml

@@ -2,7 +2,6 @@ version: '2'
 
 volumes:
   sockets:
-    driver: local
     external: true
   postgres_data:
     driver: local