Issue #3306630: [PP-1] Split the core 9.5.x ckeditor history into a new 1.0.x...

    parent::doInstall();

    // TRICKY: ::checkRequirements() runs too early.

    $existing_updates = Database::getConnection()->select('key_value')

      ->fields('key_value', ['value'])

      ->condition('collection', 'post_update')

      ->condition('name', 'existing_updates')

    $extensions = Database::getConnection()->select('config')

      ->fields('config', ['data'])

      ->condition('collection', '')

      ->condition('name', 'core.extension')

      ->execute()

      ->fetchField();

    $existing_updates = unserialize($existing_updates);

    if (in_array('ckeditor_post_update_omit_settings_for_disabled_plugins', $existing_updates, TRUE)) {

      $this->markTestSkipped('The ckeditor_post_update_omit_settings_for_disabled_plugins() post-update hook has already been applied to this database fixture.');

    $extensions = unserialize($extensions);

    if (!array_key_exists('ckeditor', $extensions['module'])) {

      $this->markTestSkipped('The CKEditor (4) module has already been uninstalled for this database fixture.');

    }

  }