I'm attaching a patch implementing super.__setattr__ (and __delattr__).

The implementation in the patch only works, if super can find a data descriptor in the MRO, otherwise it throws an AttributeError. As it can be seen in the tests, in some cases this may result in counter-intuitive behaviour. But I wasn't able to find another behaviour, that is consistent with both super.__getattr__ and normal __setattr__ semantics.