title: Can't make Symfony 2 UniqueEntity work
body: <p>I am trying to use UniqueEntity validation in my Entity, but it does not work. I have read for hours and I still did not find a solution. I guess it's something easy to see, but I've never used it before.</p>
  
  <p>When I persist a new Entity/record in database with the same data it breaks to SQL error or if there is no Unique index on the table column, record gets inserted.</p>
  
  <p>Here is my Entity </p>
  
  <p><a href="http://pastebin.com/EwsT5QGy" rel="nofollow">http://pastebin.com/EwsT5QGy</a></p>
  
  <p>Any help is welcome because I seem unable to figure it out by myself :?</p>