Creating config file /etc/redmine/default/session.yml with new version
A new secret session key has been generated in /etc/redmine/default/session.yml
Populating database for redmine instance "default".
This may take a while.
rake aborted!
Please install the mysql adapter: `gem install activerecord-mysql-adapter` (cannot load such file -- mysql)

Tasks: TOP => db:migrate => environment
(See full trace by running task with --trace)
Error when running rake db:migrate, check database configuration.
dpkg: error processing redmine (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 redmine
E: Sub-process /usr/bin/dpkg returned an error code (1)