Hmm, Travis was failing on something seemingly unrelated in functional tests (https://travis-ci.org/python-gitlab/python-gitlab/jobs/652064210), so I re-opened the PR to trigger it again and now it's happy. ¯\_(ツ)_/¯

I was wondering if mayberevert() should return a commit object instead of a dict. It seems like most other update methods also just return the server response but since this creates a new resource, people might want to manipulate that new commit directly - I just didn't see any other examples (cherry_pick doesn't return anything atm).

Thanks for the MR!