Workaround more magic of setters.

master/bt5/slapos_cloud/TestTemplateItem/testSlapOSCloudConstraint.py

@@ -25,7 +25,14 @@ class TestSlapOSConstraintMixin(testSlapOSMixin):
 
 
     # required
+    try:
+      # try to drop property from object for ones, where doing
+      # edit(property=None) does not set None, but ('None',)...
       delattr(obj, property_id)
+    except AttributeError:
+      # ...but in case of magic ones (reference->default_reference)
+      # use setter to set it to None
+      obj.edit(**{property_id:None})
     self.assertTrue(consistency_message in self.getMessageList(obj))
 
     if empty_string:

master/bt5/slapos_cloud/bt/revision

-241
\ No newline at end of file
+242
\ No newline at end of file