Make PageQuerySet inherit from treebeards MP_NodeQuerySet

wagtail/wagtailcore/query.py

@@ -1,9 +1,18 @@
-from django.db.models.query import QuerySet
 from django.db.models import Q
 from django.contrib.contenttypes.models import ContentType
 
 
-class PageQuerySet(QuerySet):
+# hack to import our patched copy of treebeard at wagtail/vendor/django-treebeard -
+# based on http://stackoverflow.com/questions/17211078/how-to-temporarily-modify-sys-path-in-python
+import sys
+import os
+treebeard_path = os.path.join(os.path.dirname(__file__), '..', 'vendor', 'django-treebeard')
+sys.path.insert(0, treebeard_path)
+from treebeard.mp_tree import MP_NodeQuerySet
+sys.path.pop(0)
+
+
+class PageQuerySet(MP_NodeQuerySet):
     """
     Defines some extra query set methods that are useful for pages.
     """