change the named tuple returned by inspect.getfullargspec to have a 'kwonlydefaults' (as claimed by the docs) attribute instead of 'kwdefaults'

Fixes #4307
Reviewed by Christian
diff --git a/Lib/inspect.py b/Lib/inspect.py
index df1d4b6..3b58bd8 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -791,7 +791,7 @@
     return ArgSpec(args, varargs, varkw, defaults)
 
 FullArgSpec = namedtuple('FullArgSpec',
-    'args, varargs, varkw, defaults, kwonlyargs, kwdefaults, annotations')
+    'args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations')
 
 def getfullargspec(func):
     """Get the names and default values of a function's arguments.
diff --git a/Misc/ACKS b/Misc/ACKS
index 19a4f8a..6d380b6 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -230,6 +230,7 @@
 Peter Funk
 Geoff Furnish
 Ulisses Furquim
+Hagen Fürstenau
 Achim Gaedke
 Lele Gaifax
 Santiago Gala
diff --git a/Misc/NEWS b/Misc/NEWS
index 24afb0e..ecc808f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -19,6 +19,9 @@
 Library
 -------
 
+- Issue #4307: The named tuple that ``inspect.getfullargspec()`` returns now
+  uses ``kwonlydefaults`` instead of ``kwdefaults``.
+
 - Issue #4298: Fix a segfault when pickle.loads is passed a ill-formed input.
 
 - Issue #4283: Fix a left-over "iteritems" call in distutils.