anchor.diff:      unzip -d $out/${python.sitePackages} $src
       unzip -d $out/${python.sitePackages} ${setuptools_source}
       unzip -d $out/${python.sitePackages} ${wheel_source}
  +  '' + stdenv.lib.optionalString (python.isPy26 or false) ''
  +    unzip -d $out/${python.sitePackages} ${argparse_source}
     '';
  +
   
     patchPhase = ''
       mkdir -p $out/bin
  
positive.code:   installPhase = ''
  
      # install pip binary
      echo '${python.interpreter} -m pip "$@"' > $out/bin/pip
      chmod +x $out/bin/pip
  
      # wrap binaries with PYTHONPATH
  
negative.code:   setuptools_source = fetchurl {
      url = "https://pypi.python.org/packages/3.5/s/setuptools/setuptools-19.4-py2.py3-none-any.whl";
      sha256 = "0801e6d862ca4ce24d918420d62f07ee2fe736dc016e3afa99d2103e7a02e9a6";
    };
    argparse_source = fetchurl {
      url = "https://pypi.python.org/packages/2.7/a/argparse/argparse-1.4.0-py2.py3-none-any.whl";
      sha256 = "0533cr5w14da8wdb2q4py6aizvbvsdbk3sj7m1jx9lwznvnlf5n3";
    };
  in stdenv.mkDerivation rec {
    name = "python-${python.version}-bootstrapped-pip-${version}";
  