Issues building pants (NOTE for everyone):
I've been using Pants for 3 years now. In the past year, I've tried updating Pants a few times and always got an error (but the reason WAS NOT Pants). Fast forward one year later, I got a new computer and installed Arch Linux on it (my previous system). With a fresh install of Arch Linux, I still couldn't get Pants to install. It would hang on
Using cached psutil-5.7.0-cp38-cp38-linux_x86_64.whl
Realizing Arch Linux had issues with just building a make package, I tried to boot Arch Linux from a USB drive, log in to my account (aka chroot), and then build Pants. And it worked flawlessly. The point is that several things can be broken in your system, preventing Pants from updating or being installed. In that case, try booting from a fresh USB drive and then do your updates.