From ff48739ed0a3f366c4d56d3c86a37cbdeec600de Mon Sep 17 00:00:00 2001
From: "Aaron Hall, MBA" <aaronchall@yahoo.com>
Date: Tue, 6 Jun 2017 15:34:57 -0400
Subject: [PATCH] bpo-30463: Add an empty __slots__ to abc.ABC.

---
 Lib/abc.py           | 2 +-
 Lib/test/test_abc.py | 3 +++
 Misc/NEWS            | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Lib/abc.py b/Lib/abc.py
index 43a34a0bbde..d13a0de89b4 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -235,7 +235,7 @@ class ABC(metaclass=ABCMeta):
     """Helper class that provides a standard way to create an ABC using
     inheritance.
     """
-    pass
+    __slots__ = ()
 
 
 def get_cache_token():
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index e20e033f219..61c2876708c 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -402,6 +402,9 @@ class TestABC(unittest.TestCase):
         C()
         self.assertEqual(B.counter, 1)
 
+    def test_ABC_has___slots__(self):
+        self.assertTrue(hasattr(abc.ABC, '__slots__'))
+
 
 class TestABCWithInitSubclass(unittest.TestCase):
     def test_works_with_init_subclass(self):
diff --git a/Misc/NEWS b/Misc/NEWS
index 4b0879bee29..f043832e670 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -345,6 +345,9 @@ Extension Modules
 Library
 -------
 
+- bpo-30463: Addded empty __slots__ to abc.ABC.  This allows subclassers
+  to deny __dict__ and __weakref__ creation.  Patch by Aaron Hall.
+
 - bpo-30520: Loggers are now pickleable.
 
 - bpo-30557: faulthandler now correctly filters and displays exception codes