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

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

<?xml version="1.0" encoding="utf-8"?>
<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="service_container" class="Symfony\Component\DependencyInjection\ContainerInterface" public="true" synthetic="true"/>
    <service id="foo" autoconfigure="true" abstract="true">
      <argument type="service" id="bar" on-invalid="ignore_uninitialized"/>
    </service>
    <service id="Psr\Container\ContainerInterface" alias="service_container" public="false"/>
    <service id="Symfony\Component\DependencyInjection\ContainerInterface" alias="service_container" public="false"/>
  </services>
</container>