Make Hydra evaluation work properly

README.md

@@ -892,15 +892,17 @@ want to test for.
 We can compose tests in the following Nix expression:
 
 ```nix
-{ pkgs ? import <nixpkgs> { inherit system; }
+{ nixpkgs ? <nixpkgs>
 , system ? builtins.currentSystem
 , processManagers ? [ "supervisord" "sysvinit" "systemd" "docker" "disnix" "s6-rc" ]
 , profiles ? [ "privileged" "unprivileged" ]
 }:
 
 let
+  pkgs = import nixpkgs { inherit system; };
+
   testService = import ../../nixproc/test-driver/universal.nix {
-    inherit system;
+    inherit nixpkgs system;
   };
 in
 {

release.nix

@@ -18,7 +18,7 @@ rec {
     };
 
     services = import ./tests/services {
-      inherit pkgs system;
+      inherit nixpkgs system;
     };
 
     multi-process-images = import ./tests/multi-process-images.nix {

tests/services/default.nix

@@ -1,12 +1,14 @@
-{ pkgs ? import <nixpkgs> { inherit system; }
+{ nixpkgs ? <nixpkgs>
 , system ? builtins.currentSystem
 , processManagers ? [ "supervisord" "sysvinit" "systemd" "docker" "disnix" "s6-rc" ]
 , profiles ? [ "privileged" "unprivileged" ]
 }:
 
 let
+  pkgs = import nixpkgs { inherit system; };
+
   testService = import ../../nixproc/test-driver/universal.nix {
-    inherit system;
+    inherit nixpkgs system;
   };
 in
 {