fix migration

netbox/dcim/migrations/0226_modulebay_rebuild_tree.py

@@ -1,12 +1,11 @@
 from django.db import migrations
-import mptt
 import mptt.managers
+import mptt.models
 
 
 def rebuild_mptt(apps, schema_editor):
     """
-    Rebuild the MPTT tree for ModuleBay to apply new ordering by 'name'
-    instead of 'module'.
+    Rebuild the MPTT tree for ModuleBay to apply new ordering.
     """
     ModuleBay = apps.get_model('dcim', 'ModuleBay')
 
@@ -14,11 +13,10 @@ def rebuild_mptt(apps, schema_editor):
     class MPTTMeta:
         order_insertion_by = ('module', 'name',)
 
-    ModuleBay.MPTTMeta = MPTTMeta
+    ModuleBay._mptt_meta = mptt.models.MPTTOptions(MPTTMeta, ModuleBay)
 
     manager = mptt.managers.TreeManager()
     manager.model = ModuleBay
-    mptt.register(ModuleBay)
     manager.contribute_to_class(ModuleBay, 'objects')
     manager.rebuild()