Updated Drupal to 8.6. This goes with the following updates because it's possible...

[yaffs-website] / web / core / modules / views / templates / views-view-row-opml.html.twig

{#
/**
 * @file
 * Default theme implementation to display an item in a views OPML feed.
 *
 * Available variables:
 * - attributes: Attributes for outline element.
 *
 * @see template_preprocess_views_view_row_opml()
 *
 * @ingroup themeable
 */
#}
    <outline{{ attributes }}/>