There does not appear to be a test for this. If so, this case may not have ever worked right. Here is the only failure at the moment (which should also be fixed).
F:\Python\dev>4\py34\pcbuild\python_d.exe -m test test_inspect
[1/1] test_inspect
test test_inspect failed -- Traceback (most recent call last):
File "F:\Python\dev\4\py34\lib\test\test_inspect.py", line 1623, in test_signature_on_builtins
test_callable(type)
File "F:\Python\dev\4\py34\lib\test\test_inspect.py", line 1604, in test_callable
signature = inspect.signature(o)
File "F:\Python\dev\4\py34\lib\inspect.py", line 1555, in signature
raise ValueError('callable {!r} is not supported by signature'.format(obj))
ValueError: callable <class 'type'> is not supported by signature