Technically a non-existent page is a "301 Moved Permanently"-type redirect to an existent page in a different variant (unless there is no such page). This affects wikis with LanguageConverter, including zh.wikipedia.
Eg. zh:匙吻鲟 (redirect=no link) is a redirect to zh:匙吻鱘, but pywikibot considers the former as an non-existent page without any information on the latter:
tools.yifeibot@tools-bastion-02:~/pywikibot$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Untracked files:
(use "git add <file>..." to include in what will be committed)
<a list of files removed>
nothing added to commit but untracked files present (use "git add" to track)
tools.yifeibot@tools-bastion-02:~/pywikibot$ python pwb.py shell
Welcome to the Pywikibot interactive shell!
>>> import pywikibot
>>> pywikibot.Page(pywikibot.Site("zh", "wikipedia"), u"匙吻鲟").exists()
False
>>> pywikibot.Page(pywikibot.Site("zh", "wikipedia"), u"匙吻鱘").exists()
True