[FBR] Upgrade to pagure 2.15.1 in prod

Good Morning Everyone, I would like to upgrade pagure in prod to 2.15.1, it's a bug fix release from 2.15 that brings upstream some of the hotfix we had to do. Changelog is something like: - Fix the requirements on straight.plugin in the requirements.txt file (Shengjing Zhu) - Fix typo in the fedmsg hook so it finds the function where it actually is - Fix and increase the logging when merging a PR - Fix pushing a merge commit to the original repo - Use psutil's Process() instead of looping through all processes (Patrick Uiterwijk) - Don't email admins for each PR conflicting - Fix/improve our new locking mechanism (Patrick Uiterwijk) - Drop making the token required at the database level since pagure-ci doesn't use one (but do flag pull-requests) - Fix the watch feature (Matt Prahl) The changes #2, #3, #4 where hotfix in prod, the last one as well but turned out the hotfix was incorrect and didn't fix the issue. My idea, if people agree, is to release 2.15.1 tomorrow morning and push it to stg then prod before the US wakes up, and rollback if something breaks. Thoughts? +1? Thanks, Pierre