Gunicorn is installed as a Python package.

Dockerfile

@@ -10,7 +10,6 @@ RUN set -ex \
 	&& apt-get update -q \
 	&& apt-get install -y -q --no-install-recommends \
       supervisor \
-      gunicorn \
       redis-server \
       libsndfile1 \
       ffmpeg \

docs/installation-production.md

@@ -27,7 +27,6 @@ Additionally you'll need these system packages:
 ```bash
 apt-get install \
     supervisor \
-    gunicorn \
     redis-server \
     libsndfile1 \
     ffmpeg \