I'm merging this without review as an emergency measure because, without it, the code is mostly unusable and because actions, such as web site deployment, fail.

A second set of eyes would still be useful here though.

Ack on the pin for typeguard. I also don't mind the version pin on filelock and psutil, but what is the rationale? Do you consider pinned versions more reliable / reproducible / stable in general?

I'm trying to avoid the same problem happening in the future with filelock and psutil and I think "compatible version" (i.e. ~=) is a reasonable solution that still allows security/stability updates.