protected function checkRequirements() {
    if (!$this->getInspector()->commandExists("vagrant")) {
      $this->logger->error("Vagrant is not installed.");
      $this->say("Please install all dependencies for Drupal VM by following the Quickstart Guide:");
      $this->say("https://github.com/geerlingguy/drupal-vm#quick-start-guide");
      throw new BltException("Drupal VM requirements are missing.");
    }
    else {
      $this->installVagrantPlugin('vagrant-hostsupdater');
    }
  }