title: Symfony try project in prod environment leads me to an error
body: <p>I was trying to run my project for the first time in a production environment I did not go how I expected.</p>
  
  <p>After following the instructions from here
  <a href="https://symfony.com/doc/current/deployment.html" rel="nofollow noreferrer">https://symfony.com/doc/current/deployment.html</a> I got an error in my <code>localhost/Symfony/web/app_dev.php</code> page :</p>
  
  <pre><code>ClassNotFoundException: Attempted to load class "SensioGeneratorBundle" from namespace     "Sensio\Bundle\GeneratorBundle" in D:\logiciel\wamp\www\Symfony\app\AppKernel.php line 28. Do you need     to "use" it from another namespace?
  </code></pre>
  
  <p>Is it possible that composer made a mistake or something? I really don't know how to solve this</p>