Changing "en" to "pt" in the URL
https://en.wikipedia.org/w/index.php?title=Special:Categories&offset=&limit=500
opens a page with a fatal error on Portuguese Wikipedia:
https://pt.wikipedia.org/w/index.php?title=Special:Categories&offset=&limit=500
[WRmslwpAICoAAD4M2RoAAAAC] 2017-05-15 13:26:47: Exceção fatal do tipo "Wikimedia\Assert\ParameterAssertionException"