JP is right, the rec isn't needed anymore

morph/grid/local/grid.nix

 # Load the helper function and call it with arguments tailored for the local
 # grid.  It will make the morph configuration for us.  We share this function
 # with the production grid and have one fewer possible point of divergence.
-import ../../lib/make-grid.nix rec {
+import ../../lib/make-grid.nix {
   name = "LocalDev";
   config = ./config.json;
   nodes = cfg: