public function update_8009000() {
    $project_yml = $this->updater->getProjectYml();
    if (!empty($project_yml['behat']['launch-phantomjs']) && $project_yml['behat']['launch-phantomjs']) {
      $project_yml['behat']['web-driver'] = 'phantomjs';
    }
    else {
      $project_yml['behat']['web-driver'] = 'selenium';
    }
    unset($project_yml['behat']['launch-selenium']);
    unset($project_yml['behat']['launch-phantomjs']);

    if (!empty($project_yml['multisite.name'])) {
      $project_yml['multisites'][] = $project_yml['multisite.name'];
      unset ($project_yml['multisite.name']);
    }
    unset($project_yml['import']);

    if (file_exists($this->updater->getRepoRoot() . '/Vagrantfile')) {
      $project_yml['vm']['enable'] = TRUE;
    }

    $this->updater->writeProjectYml($project_yml);

    $messages = [
      "You have updated to a new major version of BLT, which introduces backwards-incompatible changes.",
      "You may need to perform the following manual update steps:",
      "  - View the full list of commands via `blt list`, <comment>BLT commands have changed</comment>",
      "  - Re-initialize default Travis CI configuration via `blt recipes:ci:travis:init`.
         - Re-initialize default Acquia Pipelines configuration via `blt recipes:ci:pipelines:init`.",
      "  - Port custom Phing commands to Robo. All Phing commands are now obsolete. See:",
      "    http://blt.readthedocs.io/en/9.x/readme/extending-blt/",
    ];
    if (file_exists($this->updater->getRepoRoot() . '/blt/composer.overrides.json')) {
      $messages[] = "  - <comment>blt/composer.overrides.json</comment> is no longer necessary.";
      $messages[] = "  -  Move your overrides to your root composer.json, and set extra.merge-plugin.ignore-duplicates to true.";
    }
    $formattedBlock = $this->updater->getFormatter()->formatBlock($messages, 'ice');
    $this->updater->getOutput()->writeln("");
    $this->updater->getOutput()->writeln($formattedBlock);
    $this->updater->getOutput()->writeln("");
  }