# File lib/openid/server.rb, line 894
      def encode_to_url
        return_to = @query['openid.return_to']
        unless return_to
          raise ArgumentError, 'No return_to in query'
        end
        
        args = {
          'openid.mode' => 'error',
          'openid.error' => self.to_s
        }
        
        return OpenID::Util.append_args(return_to, args)
      end