new_contents: class IcsError(Exception):
      """
      Unknown ics error
      """
  
      def __str__(self):
          doc = self.__doc__.strip()
          return ': '.join([doc] + [str(a) for a in self.args])
  
  class NotFoundError(IcsError):
      """
      No data found
      """
      def handle(self):
          raise tornado.web.HTTPError(404, self.__doc__.strip())
  
  class CannotParsedError(IcsError):
      """
      Data cannot be parsed
      """
      def handle(self):
          raise tornado.web.HTTPError(500, self.__doc__.strip())
  
  
subject: Add exceptions in exc.py