Fixed #8291 -- Allowed 'pk' to be used as an ordering option in Model.Meta. Thanks to peterd12 for the report and to evan_schulz, gruszczy, frog32 and David Gouldin for their work on the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17445 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/management/validation.py

@@ -283,6 +283,11 @@ def get_validation_errors(outfile, app=None):
                 # this format would be nice, but it's a little fiddly).
                 if '__' in field_name:
                     continue
+                # Skip ordering on pk, this is always a valid order_by field
+                # but is an alias and therefore won't be found by
+                # opts.get_field.
+                if field_name == 'pk':
+                    continue
                 try:
                     opts.get_field(field_name, many_to_many=False)
                 except models.FieldDoesNotExist: