title: Have run laravel docker shift from 5.3 to 5.4 and 5.4 to 5.5 with problems
body: <p>When running composer update it works until @php artisan package:discover
  I then got:
  In ProviderRepository.php line 208:
  Class 'Barryvdh\Cors\ServiceProvider' not found<br />
  Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1</p>
  <p>I got Barryvdh\Cors\ServiceProvider class defined in app.php
  <a href="https://i.stack.imgur.com/KIkGy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KIkGy.png" alt="enter image description here" /></a></p>
  <p>So php artisan does not work at all. So what could be the problem?</p>