docker-compose: no gunicorn when trying "up" container
The main problem I see is that you're using image: mysitecatalogweb_source for your mysite service, and expecting that to include the committed result of running bin/install, which wasn't actually committed to the mysitecatalogweb_source image -- it's sitting in a container instead, so the virtualenv was never created in the second mysite container, and is thus not activated and gunicorn is not available. From just the snippet here, it appears that you ought to add RUN bin/install to your Dockerfile so that the virtualenv is set up before the attempt to use it.