CD is broken

See a recent pipeline for the develop branch, eg https://whetstone.private.storage/privatestorage/PrivateStorageio/-/jobs/16978

It fails to determine a version of nixpkgs to use:

++ nix eval '(import /home/deployment/PrivateStorageio/nixpkgs.nix { }).path'
error: experimental Nix feature 'nix-command' is disabled; use '--extra-experimental-features nix-command' to override
+ export NIX_PATH=nixpkgs=
+ NIX_PATH=nixpkgs=

And then fails to notice it has failed to determine a version, keeps going, and blows up when it doesn't have a compatible nixpkgs.