Python 3.7 in Arch Linux
Arch Linux updated Python 3 to version 3.7. Therefore, Python aur packages have to be rebuilt in order to continue working.
In case of pacserve run:
aurman -S --rebuild python3-threaded_servers
to rebuild and reinstall the necessary python package.
Then restart the pacserve server:
sudo systemctl start pacserve.service
You can list and rebuild all packages which need to be updated with these commands:
pacman -Qqo /usr/lib/python3.6/site-packages/* | sort -u aurman -S --rebuild --noconfirm <package>