title: Symfony assetic issue file does not exist
body: <p>I tried to resolve my problem all this morning but I didn't find the solution anywhere.</p>
  
  <p>I have a Symfony project and I use Assetic for my css and js files. 
  Till today when I ran <code>php bin/console assetic:dump --env=prod</code>, it worked fine.</p>
  
  <p>But now I have this error :   </p>
  
  <blockquote>
    <p>[Symfony\Component\Config\Exception\FileLocatorFileNotFoundException]
    The file "C:\wamp\www\PLIE08\app/config/config_=prod.yml" does not exist.</p>
  </blockquote>
  
  <p>I don't understand why it adds <code>=</code> in my file.
  Moreover, after running this command I realized that a folder called "=prod" is created in var/cache in addition to the dev and prod folder.</p>
  
  <p>I tried to update, install composer, clear the cache, look in config file if something was wrong but I'm still blocked...</p>
  
  <p>Somebody can tell me why it searchs the bad file ? </p>
  
  <p>Thanks </p>