SQL Bug on install

[katinka]

We got following error on installing this plugin to redmine 2.3.1

git clone https://github.com/tdvsdv/usability.git
Cloning into usability...
remote: Reusing existing pack: 609, done.
remote: Counting objects: 8, done.
remote: Compressing objects: 100% (7/7), done.
remote: Total 617 (delta 2), reused 0 (delta 0)
Receiving objects: 100% (617/617), 237.46 KiB | 281 KiB/s, done.
Resolving deltas: 100% (236/236), done.

rake redmine:plugins:migrate NAME=usability
(in /var/www/redmine)
rake aborted!
/var/www/redmine/plugins/usability/lib/usability/user_patch.rb:27: syntax error, unexpected '.', expecting kEND
.joins({:issues => :journals})
^
/var/www/redmine/plugins/usability/lib/usability/user_patch.rb:28: syntax error, unexpected '.', expecting kEND
.where("#{Journal.table_name}.u...
^
/var/www/redmine/plugins/usability/lib/usability/user_patch.rb:29: syntax error, unexpected '.', expecting kEND
.group("#{Project.table_name}.id")
^
/var/www/redmine/plugins/usability/lib/usability/user_patch.rb:30: syntax error, unexpected '.', expecting kEND
.order("count DESC")
^
/var/www/redmine/plugins/usability/lib/usability/user_patch.rb:31: syntax error, unexpected '.', expecting kEND
.try(:first)
^
/var/www/redmine/plugins/usability/init.rb:34:in `_callback_before_103'
/var/www/redmine/config/environment.rb:14
Tasks: TOP => redmine:plugins:migrate => environment
(See full trace by running task with --trace)