docs: def handle_an_error():
      """Will be run if the async task raises an unhandled exception."""
      import os
  
      from furious.context import get_current_async
  
      async = get_current_async()
      async_exception = async.result.payload
      exc_info = async_exception.traceback
      logging.info('async job blew up, exception info: %r', exc_info)
  
      retries = int(os.environ['HTTP_X_APPENGINE_TASKRETRYCOUNT'])
      if retries < 2:
          raise Exception(async_exception.error)
      else:
          logging.info('Caught too many errors, giving up now.')