anchor.diff:  
       "iso8601" = python.mkDerivation {
         name = "iso8601-0.1.12";
  -      src = pkgs.fetchurl { url = "https://files.pythonhosted.org/packages/45/13/3db24895497345fb44c4248c08b16da34a9eb02643cea2754b21b5ed08b0/iso8601-0.1.12.tar.gz"; sha256 = "49c4b20e1f38aa5cf109ddcd39647ac419f928512c869dc01d5c7098eddede82"; };
  -      doCheck = commonDoCheck;
  -      checkPhase = "";
  -      installCheckPhase = "";
  -      buildInputs = commonBuildInputs;
  -      propagatedBuildInputs = [ ];
  -      meta = with pkgs.stdenv.lib; {
  -        homepage = "";
  +      src = pkgs.fetchurl {
  +        url = "https://files.pythonhosted.org/packages/45/13/3db24895497345fb44c4248c08b16da34a9eb02643cea2754b21b5ed08b0/iso8601-0.1.12.tar.gz";
  +        sha256 = "49c4b20e1f38aa5cf109ddcd39647ac419f928512c869dc01d5c7098eddede82";
  +};
  +      doCheck = commonDoCheck;
  +      buildInputs = commonBuildInputs ++ [ ];
  +      propagatedBuildInputs = [ ];
  +      meta = with pkgs.stdenv.lib; {
  +        homepage = "https://bitbucket.org/micktwomey/pyiso8601";
           license = licenses.mit;
           description = "Simple module to parse ISO 8601 dates";
         };
  
positive.code: 
      "importscan" = python.mkDerivation {
        name = "importscan-0.1";
        src = pkgs.fetchurl { url = "https://files.pythonhosted.org/packages/2d/e1/01431f1afc930befc4a1e32b39e5227124ebcd5ee165683b0d8e80fdb45f/importscan-0.1.tar.gz"; sha256 = "5c003afe8d7f48d684bc9f66e8109952234812b225be324ce572ce4278b18f10"; };
        doCheck = commonDoCheck;
        checkPhase = "";
        installCheckPhase = "";
        buildInputs = commonBuildInputs;
        propagatedBuildInputs = [ ];
        meta = with pkgs.stdenv.lib; {
          homepage = "";
          license = licenses.bsdOriginal;
          description = "Recursively import modules and sub-packages";
        };
  
negative.code:       __old = pythonPackages;
        inherit interpreter;
        inherit interpreterWithPackages;
        mkDerivation = args: pythonPackages.buildPythonPackage (args // {
          nativeBuildInputs = (args.nativeBuildInputs or []) ++ args.buildInputs;
        });
        packages = pkgs;
        overrideDerivation = drv: f:
          pythonPackages.buildPythonPackage (
  