inspect.signature fails on some functions which use Argument Clinic. For example after applying issue20133 or issue20151 it fails for audioop.ratecv and binascii.a2b_qp.

>>> inspect.signature(audioop.ratecv)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 1468, in signature
    return Signature.from_builtin(obj)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 1989, in from_builtin
    p(name, default)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 1982, in p
    default = default.n
AttributeError: type object '_empty' has no attribute 'n'