Type hint that a function never returns

Even though “PEP 484 — Type Hints” standard mentioned both in question and in the answer yet nobody quotes its section: The NoReturn type that covers your question.

Quote:

The typing module provides a special type NoReturn to annotate functions that never return normally. For example, a function that unconditionally raises an exception:

from typing import NoReturn

def stop() -> NoReturn:
    raise RuntimeError('no way')

The section also provides examples of the wrong usages. Though it doesn’t cover functions with an endless loop, in type theory they both equally satisfy never returns meaning expressed by that special type.