Turn on Timecop safe mode
Recently we've been burned by people leaving out Timecop.return
in their specs, which can lead to all sorts of subtle errors in other specs (e.g. gitlab-org/gitlab-ee#2362). We should strongly consider turning on safe mode to avoid this problem in the first place: https://github.com/travisjeffery/timecop#timecopsafe_mode
We could also consider checking the state of Timecop
after each file is finished.