no longer need South introspection rule for RichTextField

wagtail/wagtailcore/fields.py

@@ -1,15 +1,10 @@
 from __future__ import absolute_import, unicode_literals
 
 import json
-import django
 
 from django.db import models
 from django.forms import Textarea
 
-if django.VERSION < (1, 7):
-    from south.modelsinspector import add_introspection_rules
-    add_introspection_rules([], ["^wagtail\.wagtailcore\.fields\.RichTextField"])
-
 from wagtail.wagtailcore.rich_text import DbWhitelister, expand_db_html
 from wagtail.utils.widgets import WidgetWithScript