[2.1][FIX] Class not found in dump command

Fix rename PathUtils Assetic para VarUtils view: 
https://github.com/kriswallsmith/assetic/tree/bfe832e2a026301121cb5a13f36954708186cf32/src/Assetic/Util

I believe that should have a new release 2.1.4 or 2.2.  

Greetings,
Ramon