/usr/include/python3.5dm/Imaging.h is in python3-pil-dbg 4.0.0-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/python3.5dm/../python3.5m/Imaging.h
/usr/include/python3.5dm/../python3.5m/Imaging.h