Comment 2 for bug 1426868

I came up with a very simple (and probably slow) patch. It could be improved, but I don’t really know how to implement this with a good performance, as my experience with how well cython translates certain python constructs is about zero. So I did not even try.

The idea is that the ordering of the namespaces is now based on the prefix name only, and due to the structure of the new_namespaces array, the prefixless namespace is sorted as if its prefix was "xmlns".