This docker container uses the Blender Cloud image, but a different entry
point. It is not intended to be network-reachable from the outside world.
All it needs are connections to the databases (mongo, redis, rabbit).
This replaces bash with the docker command, freeing memory and
automatically returning the exit code of the docker command as the exit
code of the shell script.
1_base: builds a base image, based on Ubuntu 16.10
2_buildpy: builds two images:
2a: an image that can build Python 3.6
2b: an image that contains the built Python 3.6 in /opt/python
3_buildwheels: builds an image to build wheel files, puts them in ../4_run
4_run: the production runtime image, which can't build anything and just runs.
