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_bz2.py b/Lib/test/test_bz2.py
index 58abdc1..003497f 100644
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -13,6 +13,7 @@
 import threading
 from test.support import unlink
 import _compression
+import sys
 
 
 # Skip tests if the bz2 module doesn't exist.
@@ -816,6 +817,16 @@
         # Previously, a second call could crash due to internal inconsistency
         self.assertRaises(Exception, bzd.decompress, self.BAD_DATA * 30)
 
+    @support.refcount_test
+    def test_refleaks_in___init__(self):
+        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
+        bzd = BZ2Decompressor()
+        refs_before = gettotalrefcount()
+        for i in range(100):
+            bzd.__init__()
+        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
+
+
 class CompressDecompressTest(BaseTest):
     def testCompress(self):
         data = bz2.compress(self.TEXT)