Get PS packages from PS packages.

nixos/modules/tests/private-storage.nix

@@ -87,6 +87,9 @@ let
       # succeed() is not success but 1 is.
       1;
       ";
+
+  pspkgs = import ../../../nixpkgs-ps.nix { };
+
 in {
   # https://nixos.org/nixos/manual/index.html#sec-nixos-tests
   # https://nixos.mayflower.consulting/blog/2019/07/11/leveraging-nixos-tests-in-your-project/
@@ -98,7 +101,7 @@ in {
           pkgs.daemonize
           # A Tahoe-LAFS configuration capable of using the right storage
           # plugin.
-          pkgs.privatestorage
+          pspkgs.privatestorage
           # Support for the tests we'll run.
           (pkgs.python3.withPackages (ps: [ ps.requests ps.hyperlink ]))
         ];

nixos/modules/tests/tahoe.nix

-{ ... }: {
+{ ... }:
+  let
+    pspkgs = import ../../../nixpkgs-ps.nix { };
+  in {
   nodes = {
     storage = { config, pkgs, ... }: {
       imports = [
@@ -6,7 +9,7 @@
       ];
 
       services.tahoe.nodes.storage = {
-        package = pkgs.privatestorage;
+        package = pspkgs.privatestorage;
         sections = {
           node = {
             nickname = "storage";