{# ... #}

{% block body %}
{{ form_start(form, {'method': 'post', 'action': path('fos_user_registration_register'), 'attr': {'class': 'fos_user_registration_register'}}) }}
    {{ form_row(form.email, {
        attr: { class: 'some-custom-class'}
    }) }}
    {{ form_row(form.username) }}
    {{ form_row(form.plainPassword) }}
    <div>
        <input type="submit" value="{{ 'registration.submit'|trans }}" />
    </div>
{{ form_end(form) }}
{% endblock %}