title: Symfony2 - check if user has role at authentication
body: <p>I could not find anything of this particular;</p>
  
  <p>I need a simple check when a user login at the frontend, if this user has for example role: ROLE_CUSTOMER</p>
  
  <p>I need this be done in the authenticationprocess, because it must return an error, if the user dont have this role.</p>
  
  <p>Security.yml</p>
  
  <pre><code>    public:
          pattern:   ^/
          context:            site
          form_login:
              provider:       fos_userbundle
              csrf_provider:  form.csrf_provider   
              check_path:     site_login_check
              login_path:     site_login
              success_handler: authentication_handler
              failure_handler: authentication_handler                
          logout:
              path:           site_logout
              target:         site_login
          anonymous: true   
  </code></pre>