Python 3.8's new math.hypot function also appears to suffer from the same issue as math.log:

>>> import math, inspect
>>> inspect.signature(math.hypot)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Program Files\Python38\lib\inspect.py", line 3093, in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
  File "C:\Program Files\Python38\lib\inspect.py", line 2842, in from_callable
    return _signature_from_callable(obj, sigcls=cls,
  File "C:\Program Files\Python38\lib\inspect.py", line 2296, in _signature_from_callable
    return _signature_from_builtin(sigcls, obj,
  File "C:\Program Files\Python38\lib\inspect.py", line 2107, in _signature_from_builtin
    raise ValueError("no signature found for builtin {!r}".format(func))
ValueError: no signature found for builtin <built-in function hypot>

Possibly related to issue29299?

This isn't a bug.  It is a known limitation of the ArgumentClinic that it cannot currently describe functions with *args.   That and other limitations is also why we don't have signatures for min() max() range() etc.