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

[yaffs-website] / vendor / symfony / dependency-injection / Tests / Fixtures / xml / services7.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
  <services>
    <service id="foo" class="BarClass" />
  </services>
</container>