use python testing from stable nixpkgs

test/make-test.nix

@@ -1,25 +1,12 @@
 testArgs:
 
 let
-  stablePkgs = import <nixpkgs> { config = {}; overlays = []; };
-  unstable = (import ../pkgs/nixpkgs-pinned.nix).nixpkgs-unstable;
+  pkgs = import <nixpkgs> { config = {}; overlays = []; };
 
-  # Stable nixpkgs doesn't yet include the Python testing framework.
-  # Use unstable nixpkgs and patch it so that it uses stable nixpkgs for the VM
-  # machine configuration.
-  testingPkgs =
-    stablePkgs.runCommand "nixpkgs-testing" {} ''
-    cp -r ${unstable} $out
-    cd $out
-    chmod +w -R .
-    patch -p1 < ${./use-stable-pkgs.patch}
-  '';
-
-  test = (import "${testingPkgs}/nixos/tests/make-test-python.nix") testArgs;
+  test = (import "${pkgs.path}/nixos/tests/make-test-python.nix") testArgs;
 
   fixedTest = { system ? builtins.currentSystem, ... }@args:
     let
-       pkgs = (import testingPkgs { inherit system; config = {}; overlays = []; } );
        pkgsFixed = pkgs // {
          # Fix the black Python code formatter that's used in the test to allow the test
          # script to have longer lines. The default width of 88 chars is too restrictive for
@@ -35,7 +22,7 @@ let
          # QEMU 4.20 from unstable fails on Travis build nodes with message
          # "error: failed to set MSR 0x48b to 0x159ff00000000"
          # Use version 4.0.1 instead.
-         inherit (stablePkgs) qemu_test;
+         inherit (pkgs) qemu_test;
        };
     in
       test (args // { pkgs = pkgsFixed; });

test/use-stable-pkgs.patch

@@ -1,28 +0,0 @@
---- a/nixos/lib/build-vms.nix
-+++ b/nixos/lib/build-vms.nix
-@@ -30,10 +30,10 @@ rec {
-   buildVM =
-     nodes: configurations:
- 
--    import ./eval-config.nix {
-+    import <nixpkgs/nixos/lib/eval-config.nix> {
-       inherit system;
-       modules = configurations ++ extraConfigurations;
--      baseModules =  (import ../modules/module-list.nix) ++
-+      baseModules = (import <nixpkgs/nixos/modules/module-list.nix>) ++
-         [ ../modules/virtualisation/qemu-vm.nix
-           ../modules/testing/test-instrumentation.nix # !!! should only get added for automated test runs
-           { key = "no-manual"; documentation.nixos.enable = false; }
-
-
-services.connman doesn't exist in stable nixpkgs
---- a/nixos/modules/virtualisation/qemu-vm.nix
-+++ b/nixos/modules/virtualisation/qemu-vm.nix
-@@ -620,7 +620,6 @@ in
- 
-     # Wireless won't work in the VM.
-     networking.wireless.enable = mkVMOverride false;
--    services.connman.enable = mkVMOverride false;
- 
-     # Speed up booting by not waiting for ARP.
-     networking.dhcpcd.extraConfig = "noarp";