anchor.diff:      unzip -d $out/${python.sitePackages} $src
       unzip -d $out/${python.sitePackages} ${setuptools_source}
       unzip -d $out/${python.sitePackages} ${wheel_source}
  +    # TODO: Shouldn't be necessary anymore for pip > 9.0.1!
  +    cp ${pkg_resources} $out/${python.sitePackages}/pip/_vendor/pkg_resources/__init__.py
     '';
   
     patchPhase = ''
  
positive.code: { stdenv, python, fetchPypi, makeWrapper, unzip }:
  
  let
    wheel_source = fetchPypi {
  
negative.code:     format = "wheel";
      sha256 = "f2900e560efc479938a219433c48f15a4ff4ecfe575a65de385eeb44f2425587";
    };
  
    # TODO: Shouldn't be necessary anymore for pip > 9.0.1!
    # https://github.com/NixOS/nixpkgs/issues/26392
    # https://github.com/pypa/setuptools/issues/885
    pkg_resources = fetchurl {
      url = https://raw.githubusercontent.com/pypa/setuptools/v36.0.1/pkg_resources/__init__.py;
      sha256 = "1wdnq3mammk75mifkdmmjx7yhnpydvnvi804na8ym4mj934l2jkv";
    };
  
  in stdenv.mkDerivation rec {
    pname = "pip";
    version = "9.0.1";
  