Thanks @danny-dainton for the quick reply.
The french text which I had copied for the assertion was from a web page.
Then I just tried to copy the text from the json response of postman (and not via web page)…surprisingly doing this solved my issue.
But, I am still not able to figure out the reason why it was failing with the text from the web page…Both the texts were exactly the same (at least visually)…