contiago-toolbar/app/containers/NotFoundPage/messages.js

One of the options for outputting content from contiago xml-server

/*
 * NotFoundPage Messages
 *
 * This contains all the text for the NotFoundPage component.
 */
import { defineMessages } from 'react-intl';

export default defineMessages({
  header: {
    id: 'boilerplate.containers.NotFoundPage.header',
    defaultMessage: 'Page not found.',
  },
});