Redmine

Hi all, i'm trying to set up an email reminder when issue ovedrue. i follow this wiki RedmineReminderEmails but if i try to launch it, command say me that bundle is a command not found. So i try to make it with a script such as this:

cd /opt/bitnami/apps/redmine/htdocs
bin/rake redmine:send_reminders days=0 RAILS_ENV="production"

but it doesn't go anyway. Now it say me:

/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- bundler/setup (LoadError)
        from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
        from bin/rake:15:in `<main>'

i try to install bundler with : sudo gem install bundler
It install correct but nothing change.

Help me pls

Cristian