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

[yaffs-website] / web / core / modules / taxonomy / tests / modules / taxonomy_test / taxonomy_test.info.yml

name: 'Taxonomy test'
type: module
description: 'Provides test hook implementations for taxonomy tests'
package: Testing
version: VERSION
core: 8.x
dependencies:
  - drupal:taxonomy