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/concurrent/futures/_base.py

@@ -544,7 +544,7 @@ class Future(object):
 class Executor(object):
     """This is an abstract base class for concrete asynchronous executors."""
 
-    def submit(self, fn, *args, **kwargs):
+    def submit(*args, **kwargs):
         """Submits a callable to be executed with the given arguments.
 
         Schedules the callable to be executed as fn(*args, **kwargs) and returns
@@ -553,6 +553,19 @@ class Executor(object):
         Returns:
             A Future representing the given call.
         """
+        if len(args) >= 2:
+            pass
+        elif not args:
+            raise TypeError("descriptor 'submit' of 'Executor' object "
+                            "needs an argument")
+        elif 'fn' in kwargs:
+            import warnings
+            warnings.warn("Passing 'fn' as keyword argument is deprecated",
+                          DeprecationWarning, stacklevel=2)
+        else:
+            raise TypeError('submit expected at least 1 positional argument, '
+                            'got %d' % (len(args)-1))
+
         raise NotImplementedError()
 
     def map(self, fn, *iterables, timeout=None, chunksize=1):