python manage.py distill-local returns exit status 0 on failure

There have been a few failures to build, which havent been seen because `python manage.py distill-local` doesnt return a non-zero exit status.

https://github.com/coala/community/issues/19 is one such occurrence, which was with Django 2.

Here is the same occurring when using Django <2.0

https://travis-ci.org/jayvdb/coala_community/builds/311125722#L1182