> you could give some kind of command-line flag

That already exists -- set PYTHONHASHSEED=0.

> But I'll let someone else have the joys of negotiating with Lennart, and I won't blame the Python devs if using GRND_NONBLOCK unconditionally is less painful than having to work with the systemd folks. 

In case it's of any relief: This has nothing to do with having to change anything in systemd itself -- none of the services that systemd ships use Python. The practical case where this bug appeared was cloud-init (which is written in Python), and that wants to run early in the boot sequence even before the network is up (so that tools like "pollinate" which gather entropy from the cloud host don't kick in yet). So if there's any change needed at all, it would be in cloud-init and similar services which run Python during early boot.