Based on tutorial from https://medium.com/@angellom/automatically-building-a-flask-docker-image-on-git-push-with-jenkins-5a30c9fc9beb
Also based on https://blog.jetbrains.com/pycharm/2017/03/docker-compose-getting-flask-up-and-running/
Understanding volumes: https://container-solutions.com/understanding-volumes-docker/
Change #1