fix admin-sortable update

aircox/admin/episode.py

@@ -3,6 +3,7 @@ from copy import copy
 from django.contrib import admin
 from django.forms import ModelForm
 from django.utils.translation import gettext as _
+from adminsortable2.admin import SortableAdminBase
 
 from ..models import Episode, Diffusion
 
@@ -56,7 +57,7 @@ class EpisodeAdminForm(ModelForm):
 
 
 @admin.register(Episode)
-class EpisodeAdmin(PageAdmin):
+class EpisodeAdmin(SortableAdminBase, PageAdmin):
     form = EpisodeAdminForm
     list_display = PageAdmin.list_display
     list_filter = tuple(f for f in PageAdmin.list_filter if f != 'pub_date') + \