devise_for :users, :controllers => { :sessions => "users/sessions" ,:omniauth_callbacks => "users/omniauth_callbacks" } do
    post   "users/confirmation",          :to => "devise/confirmations#create"
    get    "users/confirmation/new",      :to => "devise/confirmations#new", :as => "new_confirmation"
    get    "users/confirmation",          :to => "devise/confirmations#show"
  end
  resources :pensioners #, :only => [:index, :destroy, :new]
  resources :users #, :only => [:index, :destroy, :new]

....
   user_confirmation POST   /users/confirmation(.:format) devise/confirmations#create

   new_user_confirmation GET    /users/confirmation/new(.:format) devise/confirmations#new

                  GET    /users/confirmation(.:format)          devise/confirmations#show

                                                              ....

GET /users/confirmation?confirmation_token=BeELxDDq9sxpseLh8Rdn

The page you were looking for doesn't exist.
  You may have mistyped the address or the page may have moved.

class User < ActiveRecord::Base
      devise .... , :confirmable

class AddConfirmableToUsers < ActiveRecord::Migration
  def up
   add_column :users, :confirmation_token, :string
   add_column :users, :confirmed_at, :datetime
   add_column :users, :confirmation_sent_at, :datetime
   add_index :users, :confirmation_token, :unique => true
   User.update_all(:confirmed_at => Time.now)
  end
  ....

patch '/user/confirmation' => 'user/confirmations#update', :via => :patch, :as => :update_user_confirmation

devise_for :users, controllers: { registrations: 'registrations',
                                  sessions: 'sessions',
                                  confirmations: 'confirmations' }
devise_scope :user do
  # custom routes...
  get 'confirmation/sent' => 'confirmations#sent'
  patch 'users/confirmation' => 'confirmations#create'
end