Clean install of Gitlab 8.9 (not upgrade), enable Mattermost, Bad Gateway

[Nev (Matthias)]

@coreyhulen

3. sudo chown -R mattermost:mattermost /var/log/gitlab/mattermost/

Thank you for the hint… Mattermost was driving me crazy, it always crashed instantly. The only issue it had , was that it cannot write to the logfile… fixing that solved the startupcrash instantly.

Thank you !