/**
 * @var string $email
 *
 * @ORMColumn(name="email", type="string", length=255)
 * @AssertEmail()
 */
protected $email;

->add('email', EmailType::class, array('error_bubbling' => true,))

<div class="cart_row "><label for="email">E-mail</label>

            {{ form_widget(form_user.email) }}
            <p>{{ form_errors(form_user.email) }}</p>

        </div>