You should require python3.6

Get source from here : https://github.com/scrapy/cssselect
python3.6 setup.py build
sudo python3.6 setup.py install --root=/tmp/cssselect
cd /tmp/cssselect
sudo find . -not -type 'd' (Delete __pycache__ folders and files)
sudo mksquashfs cssselect/ python3.6-cssselect.tcz