anchor.diff:  { stdenv, fetchurl, pcre, libxslt, groff, ncurses, pkgconfig, readline, libedit
  -, python3, makeWrapper }:
  +, python2, python3, makeWrapper }:
   
   let
  -  common = { version, sha256, extraBuildInputs ? [] }:
  +  common = { version, sha256, python, extraNativeBuildInputs ? [] }:
       stdenv.mkDerivation rec {
         name = "varnish-${version}";
   
  
positive.code:         inherit sha256;
        };
  
        nativeBuildInputs = [ pkgconfig ];
        buildInputs = [
          pcre libxslt groff ncurses readline python3 libedit
          python3.pkgs.docutils makeWrapper
        ] ++ extraBuildInputs;
  
        buildFlags = "localstatedir=/var/spool";
  
  
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 ];
    };
  }
  