Rails 4 + Devise: Missing "admins/sign_up" route - ruby-on-rails

Question

I have a Rails app, v4, and just need ot modify some "old" code - I need to add some attributes to the admin model.
When I tried to add a new admin user and set to the browser "/admins/sign_up", I got an error message that the route doesn't exist.
Okay, so I checked all the Devise routes:
new_admin_session GET /admins/sign_in(.:format) devise/sessions#new
admin_session POST /admins/sign_in(.:format) devise/sessions#create
destroy_admin_session DELETE /admins/admin_logout(.:format) devise/sessions#destroy
admin_password POST /admins/password(.:format) devise/passwords#create
new_admin_password GET /admins/password/new(.:format) devise/passwords#new
edit_admin_password GET /admins/password/edit(.:format) devise/passwords#edit
PATCH /admins/password(.:format) devise/passwords#update
PUT /admins/password(.:format) devise/passwords#update
new_user_session GET /users/login(.:format) devise/sessions#new
user_session POST /users/login(.:format) devise/sessions#create
destroy_user_session DELETE /users/logout(.:format) devise/sessions#destroy
user_password POST /users/secret(.:format) devise/passwords#create
new_user_password GET /users/secret/new(.:format) devise/passwords#new
edit_user_password GET /users/secret/edit(.:format) devise/passwords#edit
PATCH /users/secret(.:format) devise/passwords#update
PUT /users/secret(.:format) devise/passwords#update
How is possible that the routes for a new admin sign up is missing? Did I miss something?
Anyway, how to add this missing route?
When I look to the views, I see that in admins/registrations/ is new.html.erb and there's a sign up form for a new admin.
How to display (under which URL) form and use it?
Thank you in advance.
EDIT: Routes
devise_for :admins, :path_names => {:sign_out => 'admin_logout'}
devise_for :users, :path_names => { :sign_in => 'login', :sign_out => 'logout', :password => 'secret',
:confirmation => 'verification', :unlock => 'unlock', :registration => 'register',
:sign_up => 'signup' }, :controllers => {:omniauth_callbacks => "omniauth_callbacks", :registrations => "registrations"}

Answer 1

You can add the missing /admins/sign_up route like the following:
devise_for :admins do
get '/admins/sign_up' => 'devise/registrations#new'
end
This generates this route:
new_admin_registration GET /admins/sign_up(.:format) devise/registrations#new
and should fix your problem.
Update:
Remove this from your current routes file:
devise_for :admins, :path_names => {:sign_out => 'admin_logout'}
Add this to your routes file:
devise_for :admins do
get '/admins/sign_up' => 'devise/registrations#new'
end