docs: def _http_req_user_agent(self):
          """Return the User-Agent value to specify in HTTP requests, defaulting
          to ``service/version`` if configured in the application settings,
          or if used in a consumer, it will attempt to obtain a user-agent from
          the consumer's process. If it can not auto-set the User-Agent, it
          defaults to ``sprockets.mixins.http/[VERSION]``.
  
          :rtype: str
  
          """
          # Tornado Request Handler
          try:
              return '{}/{}'.format(
                  self.settings['service'], self.settings['version'])
          except (AttributeError, KeyError):
              pass
  
          # Rejected Consumer
          if hasattr(self, '_process'):
              try:
                  return '{}/{}'.format(
                      self._process.consumer_name,
                      self._process.consumer_version)
              except AttributeError:
                  pass
          return DEFAULT_USER_AGENT