Using Devise 2.1.2 and Rails 3.2.6
I\'m doing this Q&A just in case others run into this problem because I found little and scattered documentation for it.
Devise needs these three attributes on your model. Therefore, generate the following migration and run it.
class AddLockableToExamples < ActiveRecord::Migration
def change
add_column :examples, :failed_attempts, :integer, default: 0
add_column :examples, :unlock_token, :string # Only if unlock strategy is :email or :both
add_column :examples, :locked_at, :datetime
end
end
Hope this saves someone else hours of google-fu.