Symfony 4 demo running with local server gives fatal error [closed]

I just installed the demo but I get a Fatal Error when I try to run it with the local web server. This is the log:

Nov 15 12:02:03 |DEBUG| PHP    Stack trace: 
Nov 15 12:02:03 |DEBUG| PHP    #0 /home/flm/workspace_neon/sf4-demo/vendor/symfony/dotenv/Dotenv.php(492): Symfony\Component\Dotenv\Dotenv->populate(Array, false) 
Nov 15 12:02:03 |DEBUG| PHP    #1 /home/flm/workspace_neon/sf4-demo/vendor/symfony/dotenv/Dotenv.php(65): Symfony\Component\Dotenv\Dotenv->doLoad(false, Array) 
Nov 15 12:02:03 |DEBUG| PHP    #2 /home/flm/workspace_neon/sf4-demo/vendor/symfony/dotenv/Dotenv.php(85): Symfony\Component\Dotenv\Dotenv->load('/home/flm/works...') 
Nov 15 12:02:03 |DEBUG| PHP    #3 /home/flm/workspace_neon/sf4-demo/config/bootstrap.php(17): Symfony\Component\Dotenv\Dotenv->loadEnv('/home/flm/works...') 
Nov 15 12:02:03 |DEBUG| PHP    #4 /home/flm/workspace_neon/sf4-demo/public/index.php(7): require('/home/flm/works...') 
Nov 15 12:02:03 |DEBUG| PHP    #5 /home/flm/.symfony/php/493f2362a36fdff7d64a072f34086eae4dfbaa1a-router.php(26): require('/home/flm/works...') 
Nov 15 12:02:03 |DEBUG| PHP    #6 {main} 
Nov 15 12:02:03 |DEBUG| PHP      thrown in /home/flm/workspace_neon/sf4-demo/vendor/symfony/dotenv/Dotenv.php on line 167 
Nov 15 12:02:03 |ERROR| SERVER GET  (500) / ip="127.0.0.1"```

The console gives:
```Symfony 4.3.8 (env: dev, debug: true)```