Login error messages not present in prompt object

When I attempt to login with incorrect credentials using new universal login form, I have a ‘wrong username or password’ error message displayed, which is correct.
Where is this message coming from? Shouldn’t it be a part of prompt.screen.texts object? When I do {{ prompt | json }}, there is no wrong-email-credentials or wrong-credentials text present in texts object, which I would expect to be there.

Or maybe I will rephrase my question: how can I check if there is any login error present on my universal login form?