> Instead of keeping the check, we could just unconditionally convert exceptions from the signature call to a TypeError in order to maintain compatibility with the old external behaviour.

Agreed. See the new patch (getargsspec_02.patch)

Unfortunately, we have to keep the old 'ismethod' check in place for backwards compatibility purposes.

Larry,

The attached patch contains one failing unit-test: 'inspect.signature' returns 'None' for '_testapi.docstring_no_signature'. It should instead raise a ValueError.