```ruby
class App < Sinatra::Application
  not_found do
    haml :not_found
  end

  get '/' do
    haml :index
  end

  get "/download/?" do
    haml :download
  end
end
```

Add temporary Rollbar error to index
user
```ruby
class App < Sinatra::Application
  not_found do
    haml :not_found
  end

  get '/' do
    Rollbar.error("Some error")
    haml :index
  end

  get "/download/?" do
    haml :download
  end
end
```
assistant