Use the official Python docker image instead of manually installing

[edmorley]

Currently the app Docker image is based on debian:jessie and then manually installs Python 3, which for Jessie is the slightly old Python 3.4.2.

If instead the Dockerfile were changed to use the official Python image:

• the amount of Dockerfile boilerplate could be reduced
• the build time would be quicker
• you'd have much more flexibility in Python version (since you'd no longer be relying on whatever the debian package version was)
• the image will likely also be smaller in size, given the tweaks that they perform in their Dockerfile

For a list of image tags, see: https://hub.docker.com/r/library/python/

I would recommend the slim variants, for example python:3.4-slim (for parity with the current Dockerfile, later you could switch to 3.5-slim or 3.6-slim).

[wlach]

Done now, thanks for the suggestion!

[edmorley]

You're welcome :-)