/usr/include/python3.6dm/Imaging.h is in python3-pil-dbg 5.1.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/python3.6dm/../python3.6m/Imaging.h
/usr/include/python3.6dm/../python3.6m/Imaging.h