TWIG: Symfony2: Plantilla base para RSS

base.rss.twig

<?xml version="1.0"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
    <channel>
        <title>{% block title %}{% endblock %}</title>
        <link>{% block url %}{% endblock %}</link>
        <description>{% block descripcion %}{% endblock %}</description>
 
        <language>{% block idioma %}
            {{ app.request.locale }}
        {% endblock %}</language>
 
        <pubDate>{% block fechaPublicacion %}
            {{ 'now'|date('r') }}
        {% endblock %}</pubDate>
 
        <lastBuildDate>{% block fechaCreacion %}
            {{ 'now'|date('r') }}
        {% endblock %}</lastBuildDate>
 
        <generator>Symfony2</generator>
        <atom:link href="{% block self %}{% endblock %}"
                   rel="self" type="application/rss+xml" />
        {% block items %}{% endblock %}
    </channel>
</rss>