old_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  from tornado.web import Application
  
  
  class Routers(Application):
      pass
  
new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  from tornado.web import Application
  
  
  class Routers(Application):
      debug = True
  
subject: Set debug default True in routers