module-assistant leaves old file in /var/cache/modass and never deletes
them. I have files there dated from 5 years ago!
Perhaps whenever it's going to write to there it should also clean it up.
Maybe ask the user if it should remove old build logs, but certainly it
can remove *.avail_version files, and similar automatically.
BTW I don't think buildlogs really belong in /var/cache anyway, it seems
like a violation of the FHS to me. They should probably go in /tmp or
maybe /var/log. Even simply placing them in the same directory as the
.deb would be better - that way people would actually notice them!