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

[yaffs-website] / web / core / profiles / testing_missing_dependencies / testing_missing_dependencies.info.yml

name: 'Testing missing dependencies'
type: profile
description: 'Minimal profile for running a test when dependencies are listed but missing.'
version: VERSION
core: 8.x
hidden: true
install:
  - block
  - drupal:node
  - drupal:fictional
  - missing_module1
  - missing_module2
keep_english: true