anchor.diff:  assert enableE2E -> pythonPackages.pycrypto != null;
   assert enableRST -> pythonPackages.docutils != null;
   assert enableSpelling -> gtkspell != null;
  +assert enableNotifications -> pythonPackages.notify != null;
   assert enableLaTeX -> texLive != null;
   
   with stdenv.lib;
  
positive.code:   ] ++ optionals enableJingle [ farstream gst_plugins_bad libnice ]
      ++ optional enableE2E pythonPackages.pycrypto
      ++ optional enableRST pythonPackages.docutils
      ++ optional enableLaTeX texLive;
  
    postInstall = ''
  
negative.code: , enableE2E ? true
  , enableRST ? true
  , enableSpelling ? true, gtkspell ? null
  , enableNotifications ? false
  , enableLaTeX ? false, texLive ? null
  }:
  
  