title: Assert File not validating
body: <p>I have followed the instructions on the documentation for how to handle file upload using Doctrine.</p>
  
  <p>Image upload works fine but when I upload some other file type, it just lets the file upload even if I have properly set the annotation on the $file property like this:</p>
  
  <pre><code>/**
   * @Assert\File(
   *     maxSizeMessage = "L'image ne doit pas dépasser 5Mb.",
   *     maxSize = "5000k",
   *     mimeTypes = {"image/jpg", "image/jpeg", "image/gif", "image/png"},
   *     mimeTypesMessage = "Les images doivent être au format JPG, GIF ou PNG."
   * )
   */
  public $file;
  </code></pre>