No informative error message given when merge fails due to branch rules
reference tweet: https://twitter.com/JiTe/status/1127230204521451521
User is unable to merge via the web UI, and just sees a disabled merge button with a loading icon the whole time.
Title updated as per https://gitlab.com/gitlab-org/gitlab-ce/issues/61731#note_169400677
Edited by 🤖 GitLab Bot 🤖