copy paste text in lyx document

[Wolfgang Engelmann]

If I copy and paste text from an external source into a lyx document, I 
get this error message:
  Bei der Ausführung von
python -tt $$s/scripts/html2latexwrapper.py gnuhtml2latex
"Buffer_importStringYAWZce.html" "Buffer_importStringYAWZce.tex"
ist ein Fehler aufgetreten
Its nothing serious, since ok ing it copies anyway. But would still like 
to know what I am missing. I use Debian bullseye and Lyx 2.3.3
Wolfgang