title: How to translate Symfony2 Exception
body: <p>I'm using yml format to translate my web app but I've one problem.</p>
  
  <p>What I would like to do:</p>
  
  <pre><code>#exception.en.yml
  exception.bad: 'Bad credentials'
  </code></pre>
  
  <p>What I know is possible to do:</p>
  
  <pre><code>#exception.en.yml
  'Bad credentials': 'Bad credentials'
  </code></pre>
  
  <p>Is this the only method to translate the exception?</p>