code: function onEmpty (data, env) {
    let message = `SassDoc could not find anything to document.\n
    * Are you still using \`/**\` comments ? They're no more supported since 2.0.
      See <http://sassdoc.com/upgrading/#c-style-comments>.\n`
  
    if (!data.length && env.verbose) {
      env.emit('warning', new errors.Warning(message))
    }
  }
docs: Warn user on empty documentation.
  @param {Array} data
  @param {Object} env