bug when using a custom PK name

tests/myapp/models.py

@@ -86,3 +86,13 @@ def __unicode__(self):
 
 class Student(Person):
     type = models.CharField(max_length=50)
+
+class CustomPKName(MPTTModel):
+    my_id = models.AutoField(db_column='my_custom_name', primary_key=True)
+    name  = models.CharField(max_length=50)
+    parent = models.ForeignKey('self', null=True, blank=True,
+            related_name='children', db_column="my_cusom_parent")
+
+    def __unicode__(self):
+         return self.name
+

tests/myapp/tests.py

@@ -3,7 +3,7 @@
 from django.test import TestCase
 
 from mptt.exceptions import InvalidMove
-from myapp.models import Category, Genre
+from myapp.models import Category, Genre, CustomPKName
 
 
 def get_tree_details(nodes):
@@ -346,3 +346,22 @@ class InterTreeMovementTestCase(TestCase):
 
 class PositionedInsertionTestCase(TestCase):
     pass
+
+class CustomPKNameTestCase(TestCase):
+    def setUp(self):
+        c1 = CustomPKName.objects.create(name="c1")
+        c11 = CustomPKName.objects.create(name="c11", parent=c1)
+        c12 = CustomPKName.objects.create(name="c12", parent=c1)
+
+        c2 = CustomPKName.objects.create(name="c2")
+        c21 = CustomPKName.objects.create(name="c21", parent=c2)
+        c22 = CustomPKName.objects.create(name="c22", parent=c2)
+
+        c3 = CustomPKName.objects.create(name="c3")
+
+    def test_get_next_sibling(self):
+        root = CustomPKName.objects.get(name="c12")
+        sib = root.get_next_sibling()
+        self.assertTrue(sib is None)
+
+

tests/runtests.sh

@@ -2,4 +2,4 @@
 export PYTHONPATH="./"
 export DJANGO_SETTINGS_MODULE='settings'
 
-django-admin test --pythonpath="../"
+django-admin.py test --pythonpath="../"