Reproducible test env for debian deployment
This commit adds a test-python-in-container
make target that executes our django tests in an environment that should match our default debian deployment target as well as our CI environment.
@lars @robert: please execute make test-python-in-container
and see if it works for you. The first run takes a couple of minutes to generate the test environment. Subsequent test runs take ~30 seconds on my computer.