Make config.devise available on config/application.rb

lib/devise/rails.rb

@@ -3,6 +3,8 @@ require 'devise/rails/warden_compat'
 
 module Devise
   class Engine < ::Rails::Engine
+    config.devise = Devise
+
     initializer "devise.add_middleware" do |app|
       app.config.middleware.use Warden::Manager do |config|
         Devise.configure_warden(config)