Upgrade buse to Stretch
Stretch has Ruby 2.3, that’s supported in Redmine 3.3 and newer, so #11808 (closed) must be done first.
The only other potential problem I can foresee is the MySQL → MariaDB migration, but this went fine on ecours.
Parent Task: #12160 (closed)
Related issues
- Blocks #13284
Original created by @intrigeri on 13528 (Redmine)