docs: def _download_log(self, url, output_file):
          """Saves log returned by the message bus."""
          logger.info("Saving log %s to %s", url, output_file)
  
          def _do_log_download():
              try:
                  return self.session.get(url)
              # pylint: disable=broad-except
              except Exception as err:
                  logger.error(err)
  
          # log file may not be ready yet, wait a bit
          for __ in range(5):
              log_data = _do_log_download()
              if log_data or log_data is None:
                  break
              time.sleep(2)
  
          if not (log_data and log_data.content):
              logger.error("Failed to download log file %s.", url)
              return
          with open(os.path.expanduser(output_file), "ab") as out:
              out.write(log_data.content)