Hi,
my issue was that SO_BINDTODEVICE symbol was not defined in /Lib/plat-linux2/IN.py which is generated by h2py.py.
This is because the regex is missing out include dirs with "-" in the name.
In my yocto cross build system this define is in asm-generic, don't know about other build systems. 
.../usr/include/asm-generic/socket.h:#define SO_BINDTODEVICE       25
so could you please change following regex in h2py.py (patch attached)
-p_include = re.compile('^[\t ]*#[\t ]*include[\t ]+<([a-zA-Z0-9_/\.]+)')
+p_include = re.compile('^[\t ]*#[\t ]*include[\t ]+<([a-zA-Z0-9_/\.-]+)')