Comment 6 for bug 1314401

I am working on a related fix for bug #1314240 .

What I am basically doing to fix that other bug is to move constraint validation out of the schema object constructors but into separate validate() methods. For #1314240 I need this to have more control over the context used for validation, which is important for custom constraints.
Once that is done, it should be easier to fix this bug here. So I suggest to wait for my fix for #1314240. It should be nearly done.