Currently, I'm using this approach: https://gist.github.com/zimbatm/de5350245874361762b6a4dfe5366530
However, when I copy-closure to another machine I end up with errors like this when I try to install the copied package:

[dylan@nook crank]$ nix-env -qa -f default.nix crank
error: cannot import ‘/nix/store/jn0kmxvck1bc400p1mqgvrkzssxxxzyy-nixpkgs-channels-129f8d7e999b1a1f0fceaecadca30211e34d85a6-src’, since path ‘/nix/store/04knmvwgsqki2q38i2l5sn9483yd6pbk-nixpkgs-channels-129f8d7e999b1a1f0fceaecadca30211e34d85a6-src.drv’ is not valid, at /tmp/crank/nixpin.nix:5:3
(use ‘--show-trace’ to show detailed location information)