instaling cmake getting error: "Could not build wheels for cmake which use PEP 517 and cannot be installed directly"

Question

I own a raspberry pi with centos 7 and try installing opencv. to build the dependencies it seems that I need to install cmake but i get the message:

Could not build wheels for cmake which use PEP 517 and cannot be installed directly.

I have tried installing the cmake using pip3.8 install opencv-python but then i get the message above.

What should i do? i thought about using yum install opencv but I want it to run with pip on my virtualenv on python 3.8, and the yum install only does so on my python 2.7 env.