Don't compile __pycache__ files at build time
We're now using dh-virtualenv from the Jessie backports, since https://github.com/ideascube/ci-conf/pull/11 and https://github.com/ideascube/ideascube/pull/412.
Renaming this issue to focus on the remaining part: the __pycache__
files.
The Debian policy is that the Python bytecode should not be compiled at build time, but at install time.
The new dh-virtualenv from Jessie backports might help us do this.
Do we want this? Or do we prefer continuing to do it at build time?