anchor.diff:  { stdenv, fetchurl, substituteAll
   , pkgconfig
  -, cups, zlib, libjpeg, libusb1, python2Packages, sane-backends
  +, cups, zlib, libjpeg, libusb1, python3Packages, sane-backends
   , dbus, file, ghostscript, usbutils
   , net_snmp, openssl, perl, nettools
   , bash, coreutils, utillinux
  
positive.code: assert withPlugin -> builtins.elem hplipArch pluginArches
    || throw "HPLIP plugin not supported on ${stdenv.hostPlatform.system}";
  
  python2Packages.buildPythonApplication {
    inherit name src;
    format = "other";
  
  
negative.code:     pkgconfig
    ];
  
    pythonPath = with python3Packages; [
      dbus
      pillow
      pygobject2
  