• With VDE it is possible to create a virtual network of UML machines running
  on several real computer

      # https://github.com/NixOS/nixpkgs/pull/451506
      python3 = super.python3.override {
        packageOverrides = pyfinal: pyprev: {
          pytest = pyprev.pytest.overrideAttrs {
            dontWrapPythonPrograms = false;
          };
        };
      };

  # See https://nixos.org/manual/nixpkgs/unstable/#tester-invalidateFetcherByDrvHash
  # or doc/build-helpers/testers.chapter.md
  nixosTest =
    let
      /*
        The nixos/lib/testing-python.nix module, preapplied with arguments that
        make sense for this evaluation of Nixpkgs.
      */
      nixosTesting = (
        import ../../../nixos/lib/testing-python.nix {
          inherit (stdenv.hostPlatform) system;
          inherit pkgs;
          extraConfigurations = [
            (
              { lib, ... }:
              {
                config.nixpkgs.pkgs = lib.mkDefault pkgsLinux;
              }
            )
          ];
        }
      );
    in
    test:
    let
      loadedTest = if builtins.typeOf test == "path" then import test else test;
      calledTest = lib.toFunction loadedTest pkgs;
    in
    nixosTesting.simpleTest calledTest;