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

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

name: 'Testing multilingual with English'
type: profile
description: 'Minimal profile for running tests with a multilingual installer.'
version: VERSION
core: 8.x
hidden: true
install:
  - locale
keep_english: true