AbstractController.php

<?php

private function getErrorMessages(\Symfony\Component\Form\Form $form) {      
    $errors = array();

    if ($form->hasChildren()) {
        foreach ($form->getChildren() as $child) {
            if (!$child->isValid()) {
                $errors[$child->getName()] = $this->getErrorMessages($child);
            }
        }
    } else {
        foreach ($form->getErrors() as $key => $error) {
            $errors[] = $error->getMessage();
        }	
    }

    return $errors;
}