There is nothing wrong - just do it the Manjaro way - and everything is fine.
This is not how you install packages in Manjaro
The hplip is part of the official repo and the optional dependency - when you want to use gui - is python-pyqt5 on Manjaro
sudo pacman -Syu hplip python-pyqt5
Of course you can insist on doing it your way - but then you are on your own - and should not blame Manjaro.
Judging from the other topic - I am afraid you are in for some serious headaches.
I was wondering what a newcomer - or not - to Manjaro would want to build pyqt4 for - now I am thinking this is the continuum.