Hi Andreas and Ole, The problem here stems from an old version of Cython. My recommended approach would be to build from the git tag instead of the source tarball (i.e., the version without pre-generated Cython files). I don't think the Cython-related patches that were applied since would then be necessary.
I will no longer be doing packaging work for scikit-image, so feel free to remove me from the maintainer list (I thought it had already been transferred to the science team a while ago). Best regards, Stéfan