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

[yaffs-website] / vendor / symfony / routing / Tests / Fixtures / validresource.xml

<?xml version="1.0" encoding="UTF-8" ?>

<routes xmlns="http://symfony.com/schema/routing"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/routing http://symfony.com/schema/routing/routing-1.0.xsd">

    <import resource="validpattern.xml" prefix="/{foo}" host="">
        <default key="foo">123</default>
        <requirement key="foo">\d+</requirement>
        <option key="foo">bar</option>
        <condition>context.getMethod() == "POST"</condition>
    </import>
</routes>