routes.rb

# auth 
match '/auth/:provider/callback' => 'sessions#create'
match '/auth/failure' => 'sessions#failure'
match '/signout' => 'sessions#destroy', :as => :signout
match '/signin' => 'sessions#new', :as => :signin

访问 mapppp.herokuapp.com/auth/twitter，返回 The page you were looking for doesn't exist.

没有使用 devise，只用了 omniauth 让用户选择第三方登陆。