Using python south with add_to_class()

edit

So I've added a field to the models.__init__ file using the dynamic mechanism of add_to_class()

Eg

#askbot-devel/askbot/models/__init__.py
User.add_to_class('show_interesting_tags', models.BooleanField(default = False))

I want this modification to be picked up when I run South, which I would normally do by

$ ./manage.py schemamigration askbot --auto
Nothing seems to have changed.

As you can see it doesn't pick up the changes.

Any ideas? For instance how was the field 'show_country' added to the migration?