bpo-26579: Add object.__getstate__(). (GH-2821)

Copying and pickling instances of subclasses of builtin types
bytearray, set, frozenset, collections.OrderedDict, collections.deque,
weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes
implemented as slots.

Lib/test/test_bytes.py

@@ -1940,28 +1940,30 @@ class SubclassTest:
     def test_pickle(self):
         a = self.type2test(b"abcd")
         a.x = 10
-        a.y = self.type2test(b"efgh")
+        a.z = self.type2test(b"efgh")
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             b = pickle.loads(pickle.dumps(a, proto))
             self.assertNotEqual(id(a), id(b))
             self.assertEqual(a, b)
             self.assertEqual(a.x, b.x)
-            self.assertEqual(a.y, b.y)
+            self.assertEqual(a.z, b.z)
             self.assertEqual(type(a), type(b))
-            self.assertEqual(type(a.y), type(b.y))
+            self.assertEqual(type(a.z), type(b.z))
+            self.assertFalse(hasattr(b, 'y'))
 
     def test_copy(self):
         a = self.type2test(b"abcd")
         a.x = 10
-        a.y = self.type2test(b"efgh")
+        a.z = self.type2test(b"efgh")
         for copy_method in (copy.copy, copy.deepcopy):
             b = copy_method(a)
             self.assertNotEqual(id(a), id(b))
             self.assertEqual(a, b)
             self.assertEqual(a.x, b.x)
-            self.assertEqual(a.y, b.y)
+            self.assertEqual(a.z, b.z)
             self.assertEqual(type(a), type(b))
-            self.assertEqual(type(a.y), type(b.y))
+            self.assertEqual(type(a.z), type(b.z))
+            self.assertFalse(hasattr(b, 'y'))
 
     def test_fromhex(self):
         b = self.type2test.fromhex('1a2B30')
@@ -1994,6 +1996,9 @@ class SubclassTest:
 class ByteArraySubclass(bytearray):
     pass
 
+class ByteArraySubclassWithSlots(bytearray):
+    __slots__ = ('x', 'y', '__dict__')
+
 class BytesSubclass(bytes):
     pass
 
@@ -2014,6 +2019,9 @@ class ByteArraySubclassTest(SubclassTest, unittest.TestCase):
         x = subclass(newarg=4, source=b"abcd")
         self.assertEqual(x, b"abcd")
 
+class ByteArraySubclassWithSlotsTest(SubclassTest, unittest.TestCase):
+    basetype = bytearray
+    type2test = ByteArraySubclassWithSlots
 
 class BytesSubclassTest(SubclassTest, unittest.TestCase):
     basetype = bytes