[3.9] bpo-42727: [Enum] EnumMeta.__prepare__ now accepts **kwds (GH-23917). (GH-23926)

* [3.9] [Enum] EnumMeta.__prepare__ now accepts **kwds (GH-23917).
(cherry picked from commit 6ec0adefad)

Lib/enum.py

@@ -170,7 +170,7 @@ class EnumMeta(type):
     Metaclass for Enum
     """
     @classmethod
-    def __prepare__(metacls, cls, bases):
+    def __prepare__(metacls, cls, bases, **kwds):
         # check that previous enum members do not exist
         metacls._check_for_existing_members(cls, bases)
         # create the namespace dict