anchor.diff:  { stdenv, fetchurl, pcre, libxslt, groff, ncurses, pkgconfig, readline, libedit
  -, python2, makeWrapper }:
  +, python3, makeWrapper }:
   
   let
     common = { version, sha256, extraBuildInputs ? [] }:
  
positive.code:     sha256 = "1cqlj12m426c1lak1hr1fx5zcfsjjvka3hfirz47hvy1g2fjqidq";
    };
    varnish6 = common {
      version = "6.1.1";
      sha256 = "0gf9hzzrr1lndbbqi8cwlfasi7l517cy3nbgna88i78lm247rvp0";
      extraBuildInputs = [ python2.pkgs.sphinx ];
    };
  }
  
negative.code: 
        nativeBuildInputs = [ pkgconfig ];
        buildInputs = [
          pcre libxslt groff ncurses readline python3 libedit
          python3.pkgs.docutils makeWrapper
        ] ++ extraBuildInputs;
  
        buildFlags = "localstatedir=/var/spool";
  