old_contents: import cherrypy
  import os
  
  class App(object):
      @cherrypy.expose
      def index(self):
          return "Hello World!"
  
  if __name__ == '__main__':
      cherrypy.config.update({
          'server.socket_host': '127.0.0.1',
          'server.socket_port': int(os.environ.get('PORT', '5000')),
      })
      cherrypy.quickstart(App())
  
new_contents: import cherrypy
  import os
  
  class App(object):
      @cherrypy.expose
      def index(self):
          return "Hello World!"
  
  cherrypy.config.update({
      'server.socket_host': '0.0.0.0',
      'server.socket_port': int(os.environ.get('PORT', '5000')),
  })
  cherrypy.quickstart(App())
  
subject: fix server.py for heroku