bpo-31787: Prevent refleaks when calling __init__() more than once (GH-3995)

(cherry picked from commit d019bc8319ea35e93bf4baa38098ff1b57cd3ee5)

Co-authored-by: Oren Milman <orenmn@gmail.com>
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index d24d005..0e7728e 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1559,6 +1559,15 @@
         del cm.x
         self.assertNotHasAttr(cm, "x")
 
+    @support.refcount_test
+    def test_refleaks_in_classmethod___init__(self):
+        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
+        cm = classmethod(None)
+        refs_before = gettotalrefcount()
+        for i in range(100):
+            cm.__init__(None)
+        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
+
     @support.impl_detail("the module 'xxsubtype' is internal")
     def test_classmethods_in_c(self):
         # Testing C-based class methods...
@@ -1614,6 +1623,15 @@
         del sm.x
         self.assertNotHasAttr(sm, "x")
 
+    @support.refcount_test
+    def test_refleaks_in_staticmethod___init__(self):
+        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
+        sm = staticmethod(None)
+        refs_before = gettotalrefcount()
+        for i in range(100):
+            sm.__init__(None)
+        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
+
     @support.impl_detail("the module 'xxsubtype' is internal")
     def test_staticmethods_in_c(self):
         # Testing C-based static methods...