/usr/lib/python3/dist-packages/Cython/Includes/posix/ is in cython3 0.25.2-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python3/dist-packages/Cython/Includes/posix/__init__.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/dlfcn.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/fcntl.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/ioctl.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/mman.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/resource.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/select.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/signal.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/stat.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/stdio.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/stdlib.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/strings.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/time.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/types.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/unistd.pxd
/usr/lib/python3/dist-packages/Cython/Includes/posix/wait.pxd