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