bpo-36492: Deprecate passing some arguments as keyword arguments. (GH-12637)

Deprecated passing the following arguments as keyword arguments:

- "func" in functools.partialmethod(), weakref.finalize(),
  profile.Profile.runcall(), cProfile.Profile.runcall(),
  bdb.Bdb.runcall(), trace.Trace.runfunc() and
  curses.wrapper().
- "function" in unittest.addModuleCleanup() and
  unittest.TestCase.addCleanup().
- "fn" in the submit() method of concurrent.futures.ThreadPoolExecutor
  and concurrent.futures.ProcessPoolExecutor.
- "callback" in contextlib.ExitStack.callback(),
  contextlib.AsyncExitStack.callback() and
  contextlib.AsyncExitStack.push_async_callback().
- "c" and "typeid" in the create() method of multiprocessing.managers.Server
  and multiprocessing.managers.SharedMemoryServer.
- "obj" in weakref.finalize().

Also allowed to pass arbitrary keyword arguments (even "self" and "func")
if the above arguments are passed as positional argument.

Lib/weakref.py

@@ -527,7 +527,33 @@ class finalize:
     class _Info:
         __slots__ = ("weakref", "func", "args", "kwargs", "atexit", "index")
 
-    def __init__(self, obj, func, *args, **kwargs):
+    def __init__(*args, **kwargs):
+        if len(args) >= 3:
+            self, obj, func, *args = args
+        elif not args:
+            raise TypeError("descriptor '__init__' of 'finalize' object "
+                            "needs an argument")
+        else:
+            if 'func' not in kwargs:
+                raise TypeError('finalize expected at least 2 positional '
+                                'arguments, got %d' % (len(args)-1))
+            func = kwargs.pop('func')
+            if len(args) >= 2:
+                self, obj, *args = args
+                import warnings
+                warnings.warn("Passing 'func' as keyword argument is deprecated",
+                              DeprecationWarning, stacklevel=2)
+            else:
+                if 'obj' not in kwargs:
+                    raise TypeError('finalize expected at least 2 positional '
+                                    'arguments, got %d' % (len(args)-1))
+                obj = kwargs.pop('obj')
+                self, *args = args
+                import warnings
+                warnings.warn("Passing 'obj' as keyword argument is deprecated",
+                              DeprecationWarning, stacklevel=2)
+        args = tuple(args)
+
         if not self._registered_with_atexit:
             # We may register the exit function more than once because
             # of a thread race, but that is harmless