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/contextlib.py

@@ -377,7 +377,8 @@ class _BaseExitStack:
         return MethodType(cm_exit, cm)
 
     @staticmethod
-    def _create_cb_wrapper(callback, *args, **kwds):
+    def _create_cb_wrapper(*args, **kwds):
+        callback, *args = args
         def _exit_wrapper(exc_type, exc, tb):
             callback(*args, **kwds)
         return _exit_wrapper
@@ -426,11 +427,26 @@ class _BaseExitStack:
         self._push_cm_exit(cm, _exit)
         return result
 
-    def callback(self, callback, *args, **kwds):
+    def callback(*args, **kwds):
         """Registers an arbitrary callback and arguments.
 
         Cannot suppress exceptions.
         """
+        if len(args) >= 2:
+            self, callback, *args = args
+        elif not args:
+            raise TypeError("descriptor 'callback' of '_BaseExitStack' object "
+                            "needs an argument")
+        elif 'callback' in kwds:
+            callback = kwds.pop('callback')
+            self, *args = args
+            import warnings
+            warnings.warn("Passing 'callback' as keyword argument is deprecated",
+                          DeprecationWarning, stacklevel=2)
+        else:
+            raise TypeError('callback expected at least 1 positional argument, '
+                            'got %d' % (len(args)-1))
+
         _exit_wrapper = self._create_cb_wrapper(callback, *args, **kwds)
 
         # We changed the signature, so using @wraps is not appropriate, but
@@ -536,7 +552,8 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
         return MethodType(cm_exit, cm)
 
     @staticmethod
-    def _create_async_cb_wrapper(callback, *args, **kwds):
+    def _create_async_cb_wrapper(*args, **kwds):
+        callback, *args = args
         async def _exit_wrapper(exc_type, exc, tb):
             await callback(*args, **kwds)
         return _exit_wrapper
@@ -571,11 +588,26 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
             self._push_async_cm_exit(exit, exit_method)
         return exit  # Allow use as a decorator
 
-    def push_async_callback(self, callback, *args, **kwds):
+    def push_async_callback(*args, **kwds):
         """Registers an arbitrary coroutine function and arguments.
 
         Cannot suppress exceptions.
         """
+        if len(args) >= 2:
+            self, callback, *args = args
+        elif not args:
+            raise TypeError("descriptor 'push_async_callback' of "
+                            "'AsyncExitStack' object needs an argument")
+        elif 'callback' in kwds:
+            callback = kwds.pop('callback')
+            self, *args = args
+            import warnings
+            warnings.warn("Passing 'callback' as keyword argument is deprecated",
+                          DeprecationWarning, stacklevel=2)
+        else:
+            raise TypeError('push_async_callback expected at least 1 '
+                            'positional argument, got %d' % (len(args)-1))
+
         _exit_wrapper = self._create_async_cb_wrapper(callback, *args, **kwds)
 
         # We changed the signature, so using @wraps is not appropriate, but