anchor.diff:  { releng_pkgs }:
   
   let
  -  inherit (releng_pkgs.pkgs) fetchurl mercurial cacert ;
  +  inherit (releng_pkgs.pkgs) fetchurl mercurial cacert python2Packages makeWrapper docutils unzip;
     inherit (releng_pkgs.pkgs.stdenv) mkDerivation;
  -  inherit (releng_pkgs.pkgs.lib) licenses ;
  +  inherit (releng_pkgs.pkgs.lib) licenses;
   
     hg_tools = mkDerivation {
       name = "mozilla-hg-tools";
       src = fetchurl {
  -      url = "https://hg.mozilla.org/hgcustom/version-control-tools/archive/e05bed1064ed.tar.bz2";
  -      sha256 = "1icg8cvjpw5x0xapryhmjqsmm2amzh57pnqd7r0idf6h8mphpimp";
  +      url = "https://hg.mozilla.org/hgcustom/version-control-tools/archive/825b151d379c.tar.bz2";
  +      sha256 = "0l4i3x20irshf4xa2xy64nvqi04wrj2h92bn24v2j72nqmg6379x";
       };
       installPhase = ''
         mkdir -p $out
  
positive.code:     robustcheckout = ${hg_tools}/hgext/robustcheckout/__init__.py
      EOF
    '';
  })
  
negative.code:     };
    };
  
    # Stick to 4.4 so that robustcheckout works fine
    version = "4.4";
    name = "mercurial-${version}";
  
  in python2Packages.buildPythonApplication {
    inherit name;
    format = "other";
  
    src = fetchurl {
      url = "https://mercurial-scm.org/release/${name}.tar.gz";
      sha256 = "1pl77mb7d1r0hwk571cvyq9cyjxl99q0r4d1n0imkj35fnkg8ji3";
    };
  
    buildInputs = [ makeWrapper docutils unzip ];
  
    makeFlags = [ "PREFIX=$(out)" ];
  
    postInstall = ''
      mkdir -p $out/etc/mercurial
      cat > $out/etc/mercurial/hgrc <<EOF
      [web]
  