https://bugzilla.wikimedia.org/show_bug.cgi?id=73170
--- Comment #2 from Maarten Dammers maarten@mdammers.nl --- No, it's not a normal namespace. It got some special provisions so you are allowed to connect it with namespace 0. self.crossnamespace in wikipedia_family.py needs to be updated.
If you look in https://git.wikimedia.org/blob/pywikibot%2Fcore.git/227e2be0f124f1310874cf69... for 'pt' you'll see 102 (Anexo) and 103 (talk page for Anexo).