Custom 404, 500 Templates via FeinCMS

models.py

# imports
from django.conf import settings
from django.db.models import signals
from django.dispatch import receiver
from django.test.client import Client

# your other imports, config here

@receiver(signals.post_save, sender=Page)
def error_templates(sender, instance, created, raw, using, **kwargs):
    """ needs the page to be saved 2 times, because the content types are saved after "post_save" """
    if instance.slug in ('404', '500'):
        c = Client()
        response = c.get(instance.get_absolute_url())
        response.render()
        template_path = os.path.join(settings.MEDIA_ROOT, 'cache')
        full_template_name = os.path.join(template_path, instance.slug + '.html')
        template = codecs.open(full_template_name, 'w', 'utf-8')
        template.write(response.rendered_content)
        template.close()

Or try this instead: http://komunitasweb.com/2011/06/handling-404-page-on-feincms/