Rails: Routes Issue

Rails: Routes Issue

I created new rails app and generated 3 models(Category, Course, Lesson)
and migrated.
Then created 3 controller respectively.
Then for routes i added resources in routes.rb like this:
'resources :categories'
'resources :courses'
'resources :'lessons'
But the last line 'resources :lessons' is not working giving me error
something like this
Railsapp::Application::RoutesReloader#execute_if_updated delegated to
updater.execute_if_updated
Anyone else faced the same issue ?