Method page.categories(api=True) didn't get enough results for pages with a lot of categories (for example on WP:en, with Talk:U2 or Talk:Unification of Germany, you only get the 10 first).
In fact, it's just an indentation error on the return in wikipedia.py at line 2247, which prevent the loop to get all of them.
Small patch
done in r8491. thanks