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

[yaffs-website] / web / core / modules / system / tests / modules / update_script_test / config / schema / update_script_test.schema.yml

# Schema for the configuration files of the Update Script Test module.

update_script_test.settings:
  type: config_object
  label: ''
  mapping:
    requirement_type:
      type: integer
      label: 'Requirement type'