> FWIW, I believe that you have to call `PyErr_NormalizeException` on the values returned from `PyErr_Fetch`. It looks like this is working as expected.


Indeed that is the case, from the docs:

Under certain circumstances, the values returned by PyErr_Fetch() below can be “unnormalized”, meaning that *exc is a class object but *val is not an instance of the same class. This function can be used to instantiate the class in that case. If the values are already normalized, nothing happens. The delayed normalization is implemented to improve performance.