anchor.diff:      libvirt-glib
       libxml2
       vte
  -  ] ++ optionals spiceSupport [
  +  ] ++ optionals spiceSupport ([
       gdbm
  -    libcap
       spice-gtk_libsoup2
       spice-protocol
  -  ];
  +  ] ++ optionals stdenv.isLinux [
  +    libcap
  +  ]);
   
     # Required for USB redirection PolicyKit rules file
     propagatedUserEnvPkgs = optional spiceSupport spice-gtk_libsoup2;
  
positive.code: 
    meta = {
      description = "A viewer for remote virtual machines";
      maintainers = [ maintainers.raskin ];
      platforms = platforms.linux;
      license = licenses.gpl2;
    };
    passthru = {
  
negative.code: 
  assert spiceSupport -> (
    gdbm != null
    && (stdenv.isLinux -> libcap != null)
    && spice-gtk_libsoup2 != null
    && spice-protocol != null
  );
  