these 2 derivations will be built:
  /nix/store/1a7qmcfc0w474z0n335d6h6s8y0ypmfl-nixos-test-driver-pg_cron.drv
  /nix/store/pa6z7s90512ln2aizs60rzk2rrgwg5ns-vm-test-run-pg_cron.drv