anchor.diff:          inherit sha256;
         };
   
  -      nativeBuildInputs = [ pkgconfig ];
  +      nativeBuildInputs = with python.pkgs; [ pkgconfig docutils ] ++ extraNativeBuildInputs;
         buildInputs = [
  -        pcre libxslt groff ncurses readline python3 libedit
  -        python3.pkgs.docutils makeWrapper
  -      ] ++ extraBuildInputs;
  +        pcre libxslt groff ncurses readline libedit makeWrapper python
  +      ];
   
         buildFlags = "localstatedir=/var/spool";
   
  
positive.code: { stdenv, fetchurl, pcre, libxslt, groff, ncurses, pkgconfig, readline, libedit
  , python3, makeWrapper }:
  
  let
    common = { version, sha256, extraBuildInputs ? [] }:
      stdenv.mkDerivation rec {
        name = "varnish-${version}";
  
  
negative.code:   varnish4 = common {
      version = "4.1.10";
      sha256 = "08kwx0il6cqxsx3897042plh1yxjaanbaqjbspfl0xgvyvxk6j1n";
      python = python2;
    };
    varnish5 = common {
      version = "5.2.1";
      sha256 = "1cqlj12m426c1lak1hr1fx5zcfsjjvka3hfirz47hvy1g2fjqidq";
      python = python2;
    };
    varnish6 = common {
      version = "6.2.0";
      sha256 = "0lwfk2gq99c653h5f51fs3j37r0gh2pf0p4w5z986nm2mi9z6yn3";
      python = python3;
      extraNativeBuildInputs = [ python3.pkgs.sphinx ];
    };
  }
  