Comment 3 for bug 1785502

I made it installs correctly.
Since I had a backup, I decided to reinstall completely from scratch (which didn't work at first...)

And since I don't know what was necessary and what wasn't, here is all I've done to do so:

# removed completely (answered yes to database removal)
apt remove -y redmine
apt autoremove -y
# fixed the rake problem for install
rm /usr/local/bin/rake
# reinstalled
apt install redmine
service redmine start
# it started but as a new install, will now try to restore backup...

What I know for sure is the problem is coming from the /usr/local/bin/rake file (which refers to ruby2.3)

Should give you a hint on how to fix this ;)