public override void OnException(HttpActionExecutedContext context) {
     if (context.Exception is EntityErrorsException) {
         var e = (EntityErrorsException)context.Exception;
         var error = new SaveError(e.Message, e.EntityErrors);
         var resp = new HttpResponseMessage(e.StatusCode) {
           Content = new ObjectContent(typeof(SaveError), error, JsonFormatter.Create()),
         };
         context.Response = resp;
     }
 }