/usr/include/python3.5dm/ImPlatform.h is in python3-pil-dbg 3.1.2-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/python3.5dm/../python3.5m/ImPlatform.h
/usr/include/python3.5dm/../python3.5m/ImPlatform.h