In building Genshi, an extension in C fails t build

writing manifest file 'Genshi.egg-info/SOURCES.txt'
running build_ext
building 'genshi._speedups' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3
-Wall -Wstrict-prototypes -fPIC
-I/gnu/store/alk9r3rir93pjmv8im20f8xrvv90219z-python-3.5.2/include/python3.5m
-c genshi/_speedups.c -o build/temp.linux-x86_64-3.5/genshi/_speedups.o
genshi/_speedups.c: In function ‘escape’:
genshi/_speedups.c:89:13: error: ‘PyUnicodeObject’ has no member named ‘str’
     inp = in->str;
             ^
genshi/_speedups.c:90:24: error: ‘PyUnicodeObject’ has no member named
‘length’
     while (*(inp) || in->length > inp - in->str) {
                        ^
genshi/_speedups.c:90:43: error: ‘PyUnicodeObject’ has no member named ‘str’
     while (*(inp) || in->length > inp - in->str) {
                                           ^
genshi/_speedups.c:120:13: error: ‘PyUnicodeObject’ has no member named
‘str’
     inp = in->str;
             ^
...

a looong list of missing PyUnicodeObject attributes follows

I managed to build with -K, I cded to the /tmp/build-folder and retried to
build

And this is it
...
running build_ext
building 'genshi._speedups' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3
-Wall -Wstrict-prototypes -fPIC
-I/gnu/store/alk9r3rir93pjmv8im20f8xrvv90219z-python-3.5.2/include/python3.5m
-c genshi/_speedups.c -o build/temp.linux-x86_64-3.5/genshi/_speedups.o
genshi/_speedups.c: In function ‘escape’:
genshi/_speedups.c:89:13: error: ‘PyUnicodeObject’ has no member named ‘str’
     inp = in->str;
             ^
genshi/_speedups.c:90:24: error: ‘PyUnicodeObject’ has no member named
‘length’
     while (*(inp) || in->length > inp - in->str) {
...

Am I missing anything or is Genshi at faut ?