Looking at the documentation:
https://www.parse.com/tutorials/login-and-signup-views,
https://parse.com/docs/ios/api/Classes/PFLogInViewController.html
and trying various things, as well as browsing the net;
I can’t find any way to customize this message to my taste:
“Login Error invalid login credentials”
I already made a post related to this issue: How do I customize "Login Error invalid login credentials"? with not much success.
I don’t know if that qualifies as a bug, but in case there is no solution to this problem; there is clearly something missing in the API. If anyone thinks I am missing something, please let me know.