Debian has enabled `EXTERNALLY-MANAGED` from PEP 668 which breaks `pip
install --user`. I think this is a terrible decision, understandable to
want to avoid modifications in `/usr/lib/python*/site-packages` but to
have that stop be installing packages in my home directory is a big
mistake in terms of usability. In any case this patch sets the override
flag in `pip.conf` even though I'm never actually touching the real site
packages.