this is an attempted fix that works for me in production and that reproduce the documented behaviour of old django-compressor releases.
I think this behaviour is the good one, because in the case of (for example) 500/404/... pages we don't have access to STATIC_URL or other variables, and adding default valued urls that can be uncompressable is mandatory.
Open for discussion as usual,
re-implementing default documented behaviour, fixes #241
Sorry, this was changed on purpose, we shouldn't hide errors, even if DEBUG is False.