! The bundled mysql.rb driver has been removed from Rails

i am running depot app using
http://www.javapassion.com/handsonlabs/rails_depot_app/#Exercise_1
i have mysql gem installed. but i am getting error

!!! The bundled mysql.rb driver has been removed from Rails 2.2. Please
install the mysql gem and try again: gem install mysql.
rake aborted!
no such file to load – mysql

can anyone help