anchor.diff:  , enableRST ? true
   , enableSpelling ? true, gtkspell ? null
   , enableNotifications ? false
  -, enableLaTeX ? false, texLive ? null
   }:
   
   assert enableJingle -> farstream != null && gst_plugins_bad != null
  
positive.code:   '' + optionalString enableSpelling ''
      sed -i -e 's|=.*find_lib.*|= "${gtkspell}/lib/libgtkspell.so"|'   \
        src/gtkspell.py
    '' + optionalString enableLaTeX ''
      sed -i -e "s|try_run(.'dvipng'|try_run(['${texLive}/bin/dvipng'|" \
             -e "s|try_run(.'latex'|try_run(['${texLive}/bin/latex'|"   \
             -e 's/tmpfd.close()/os.close(tmpfd)/'                      \
             src/common/latex.py
    '';
  
    buildInputs = [
  
negative.code: assert enableRST -> pythonPackages.docutils != null;
  assert enableSpelling -> gtkspell != null;
  assert enableNotifications -> pythonPackages.notify != null;
  
  with stdenv.lib;
  
  