bpo-37645: add new function _PyObject_FunctionStr() (GH-14890)



Additional note: the `method_check_args` function in `Objects/descrobject.c` is written in such a way that it applies to all kinds of descriptors. In particular, a future re-implementation of `wrapper_descriptor` could use that code.

CC @vstinner @encukou 


https://bugs.python.org/issue37645



Automerge-Triggered-By: @encukou
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
index 9d11551..7d7a3be 100644
--- a/Doc/c-api/object.rst
+++ b/Doc/c-api/object.rst
@@ -196,6 +196,7 @@
       This function now includes a debug assertion to help ensure that it
       does not silently discard an active exception.
 
+
 .. c:function:: PyObject* PyObject_Bytes(PyObject *o)
 
    .. index:: builtin: bytes