/usr/include/python3.6m/mpi4py is in python3-mpi4py 2.0.0-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/python3.6m/../../lib/python3/dist-packages/mpi4py/include/mpi4py
/usr/include/python3.6m/../../lib/python3/dist-packages/mpi4py/include/mpi4py