Reported by @Thibaut120094

Warning: file_get_contents(https://www.researchgate.net/publication/329773795_Jeanne_Calment_the_secret_of_longevity): failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests in /var/wwwroot/default/wikimedia/write/sourcetemplatesgenerator/page.php on line 126

When a non-200 code is returned by the server, we should offer a more nice error message.