[laravel-5.4] Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1

in my case the problem was into outdated "../bootstrap/cache/packages.php and services.php"

I have had to. drop those files and rerun composer install...

  Erroneous data format for unserializing 'Symfony\Component\Routing\CompiledRoute'


Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1