def primary_avatar(user, size=settings.AVATAR_DEFAULT_SIZE):
    """
    This tag tries to get the default avatar for a user without doing any db
    requests. It achieve this by linking to a special view that will do all the
    work for us. If that special view is then cached by a CDN for instance,
    we will avoid many db calls.
    """
    alt = six.text_type(user)
    url = reverse('avatar_render_primary', kwargs={'user': user, 'size': size})
    return ("""<img src="%s" alt="%s" width="%s" height="%s" />""" %
            (url, alt, size, size))
This tag tries to get the default avatar for a user without doing any db
    requests. It achieve this by linking to a special view that will do all the
    work for us. If that special view is then cached by a CDN for instance,
    we will avoid many db calls.