fixed

app/controllers/admin/application_controller.rb

@@ -1,5 +1,3 @@
-module Admin
-  class ApplicationController < ApplicationController
-    http_basic_authenticate_with name: 'admin', password: ENV['ADMIN_PASSWORD'] unless Rails.env.development?
-  end
+class Admin::ApplicationController < ApplicationController
+  http_basic_authenticate_with name: 'admin', password: ENV['ADMIN_PASSWORD'] unless Rails.env.development?
 end

app/controllers/admin/pages_controller.rb

@@ -1,4 +1,4 @@
-class PagesController < Admin::ApplicationController
+class Admin::PagesController < Admin::ApplicationController
   def map
     @supporters = Supporter.where(:coordinates.ne => nil).only(:coordinates, :support)
   end

app/controllers/admin/supporters_controller.rb

@@ -1,4 +1,4 @@
-class SupportersController < Admin::ApplicationController
+class Admin::SupportersController < Admin::ApplicationController
   def index
     @supporters = Supporter.desc(:created_at)
   end

config/routes.rb

@@ -1,5 +1,12 @@
 Rails.application.routes.draw do
   root 'supporters#new'
+  
+  namespace :admin do
+    get '/map', to: 'pages#map', as: :map
+
+    resources :supporters, only: :index
+  end
+  
   scope '/:locale' do
     get '/', to: 'supporters#new'
     resources :supporters
@@ -8,10 +15,4 @@ Rails.application.routes.draw do
   end
 
   get '/cities_autocomplete', to: 'cities_autocomplete#index', as: :cities_autocomplete
-
-  namespace :admin do
-    get '/map', to: 'pages#map', as: :map
-
-    resources :supporters, only: :index
-  end
 end