title: symfony 2 : Namespace "Acme" does not contain any mapped entities
body: <p>I am following the book and on the page <a href="http://symfony.com/doc/current/book/doctrine.html" rel="noreferrer">http://symfony.com/doc/current/book/doctrine.html</a></p>
  
  <p>While following the book I am trying to work on relationship of product and category table and  doctrine generate command is giving me following error.</p>
  
  <pre><code>php app/console doctrine:generate:entities Acme
  Generating entities for namespace "Acme"
  
  
  
    [RuntimeException]                                      
    Namespace "Acme" does not contain any mapped entities.  
  
  
  
  doctrine:generate:entities [--path="..."] [--no-backup] name
  </code></pre>
  
  <p>Thx</p>