This is because breakpoints number are class attributes. With the following change, the "./python -m test test_pdb test_pdb" is ok:

$ hg diff
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -614,6 +614,8 @@
     ...     test_function_2()
     ...     end = 1
 
+    >>> from bdb import Breakpoint; Breakpoint.next = 1
+
     >>> with PdbTestInput(['break test_function_2',
     ...                    'continue',
     ...                    'return',

Attached refleak_3.patch fixes this problem for test_next_until_return_at_return_event().