[arch-dev-public] Python 3.9 rebuilds

[Evangelos Foutras]

For the next few days we'll be doing (semi-automated) rebuilds for
Python 3.9. Please avoid adding new Python packages and starting other
rebuilds during this time.

Some PKGBUILDs were modified in /trunk to use the Python 3.9
site-packages path (among other tweaks). Building those against Python
3.8 might fail or produce incorrect packages. The affected packages
are listed in the following two commits and care should be taken when
updating them while the Python rebuild is ongoing.

https://lists.archlinux.org/pipermail/arch-commits/2020-November/843783.html
https://lists.archlinux.org/pipermail/arch-commits/2020-November/843784.html