diff -r f7c84674bdec Lib/test/regrtest.py
--- a/Lib/test/regrtest.py	Fri Jul 25 12:23:08 2014 +0300
+++ b/Lib/test/regrtest.py	Fri Jul 25 17:51:06 2014 +0200
@@ -1,4 +1,15 @@
 #! /usr/bin/env python
+import tracemalloc
+tracemalloc.start(20)
+
+def dump_object_trace(obj):
+    tb = tracemalloc.get_object_traceback(obj)
+    if tb is None:
+        return
+    print("Object %r" % (obj,))
+    for line in tb.format():
+        print(line)
+    print("")
 
 """
 Usage:
@@ -579,6 +590,9 @@ def main(tests=None, testdir=None, verbo
                 if gc.garbage:
                     print "Warning: test created", len(gc.garbage),
                     print "uncollectable object(s)."
+                    if tracemalloc.is_tracing():
+                        for obj in gc.garbage:
+                            dump_object_trace(obj)
                     # move the uncollectable objects somewhere so we don't see
                     # them again
                     found_garbage.extend(gc.garbage)