code: def auth(self):
          
          basic = parse_auth(self.environ.get('HTTP_AUTHORIZATION',''))
          if basic: return basic
          ruser = self.environ.get('REMOTE_USER')
          if ruser: return (ruser, None)
          return None
docs: HTTP authentication data as a (user, password) tuple. This
              implementation currently supports basic (not digest) authentication
              only. If the authentication happened at a higher level (e.g. in the
              front web-server or a middleware), the password field is None, but
              the user field is looked up from the ``REMOTE_USER`` environ
              variable. On any errors, None is returned.