docs: def make_user_agent_string(component=None):
      """
      Return a nice and uniform user-agent string to be used when Invenio
      act as a client in HTTP requests.
      """
      ret = "Invenio-%s (+%s; \"%s\")" % (cfg.get('CFG_VERSION'),
                                          cfg.get('CFG_SITE_URL'), cfg.get('CFG_SITE_NAME'))
      if component:
          ret += " %s" % component
      return ret