active record session store en rails 4

Nótese que en Rails 4, si uno configura en config/initializers/session_store.rb

MiApp::Application.config.session_store :active_record_store

$ rails g session_migration

te tira

`ActiveRecord::SessionStore` is extracted out of Rails into a gem. Please add `activerecord-session_store` to your Gemfile to use it. (RuntimeError)

o sea que lo movieron a una gema.

Ok, lo ponemos en el Gemfile

gem 'activerecord-session_store'

y corremos

$ bundle install
$ rails g session_migration

pero responde

$ rails g session_migration
Could not find generator session_migration.

a ver… ah, ahora es

$ rails g active_record:session_migration

     create  db/migrate/20130419205254_add_sessions_table.rb

🙂