Unfortunately PR21989 has breaking the refleaks buildbots. Example:

https://buildbot.python.org/all/#/builders/320/builds/226/steps/5/logs/stdio

To reproduce:

❯ ./python -m test test_pdb -R 3:3
0:00:00 load avg: 1.40 Run tests sequentially
0:00:00 load avg: 1.40 [1/1] test_pdb
beginning 6 repetitions
123456
.test test_pdb failed -- Traceback (most recent call last):
  File "/home/pablogsal/github/cpython/Lib/doctest.py", line 2205, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for test.test_pdb.test_pdb_breakpoints_preserved_across_interactive_sessions
  File "/home/pablogsal/github/cpython/Lib/test/test_pdb.py", line 326, in test_pdb_breakpoints_preserved_across_interactive_sessions

----------------------------------------------------------------------
File "/home/pablogsal/github/cpython/Lib/test/test_pdb.py", line 330, in test.test_pdb.test_pdb_breakpoints_preserved_across_interactive_sessions
Failed example:
    with PdbTestInput([  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
       'import test.test_pdb',
       'break test.test_pdb.do_something',
       'break test.test_pdb.do_nothing',
       'break',
       'continue',
    ]):
       pdb.run('print()')
Expected:
    > <string>(1)<module>()
    (Pdb) import test.test_pdb
    (Pdb) break test.test_pdb.do_something
    Breakpoint 1 at ...test_pdb.py:...
    (Pdb) break test.test_pdb.do_nothing
    Breakpoint 2 at ...test_pdb.py:...
    (Pdb) break
    Num Type         Disp Enb   Where
    1   breakpoint   keep yes   at ...test_pdb.py:...
    2   breakpoint   keep yes   at ...test_pdb.py:...
    (Pdb) continue
Got:
    > <string>(1)<module>()->None
    (Pdb) import test.test_pdb
    (Pdb) break test.test_pdb.do_something
    Breakpoint 1 at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:396
    (Pdb) break test.test_pdb.do_nothing
    Breakpoint 2 at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:393
    (Pdb) break
    Num Type         Disp Enb   Where
    1   breakpoint   keep yes   at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:396
    2   breakpoint   keep yes   at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:393
    (Pdb) continue
    <BLANKLINE>
----------------------------------------------------------------------
File "/home/pablogsal/github/cpython/Lib/test/test_pdb.py", line 350, in test.test_pdb.test_pdb_breakpoints_preserved_across_interactive_sessions
Failed example:
    with PdbTestInput([  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
       'break',
       'break pdb.find_function',
       'break',
       'clear 1',
       'continue',
    ]):
       pdb.run('print()')
Expected:
    > <string>(1)<module>()
    (Pdb) break
    Num Type         Disp Enb   Where
    2   breakpoint   keep yes   at ...test_pdb.py:...
    3   breakpoint   keep yes   at ...pdb.py:...
    (Pdb) clear 2
    Deleted breakpoint 2 at ...test_pdb.py:...
    (Pdb) clear 3
    Deleted breakpoint 3 at ...pdb.py:...
    (Pdb) continue
Got:
    > <string>(1)<module>()->None
    (Pdb) break
    Num Type         Disp Enb   Where
    2   breakpoint   keep yes   at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:393
    3   breakpoint   keep yes   at /home/pablogsal/github/cpython/Lib/pdb.py:94
    (Pdb) clear 2
    Deleted breakpoint 2 at /home/pablogsal/github/cpython/Lib/test/test_pdb.py:393
    (Pdb) clear 3
    Deleted breakpoint 3 at /home/pablogsal/github/cpython/Lib/pdb.py:94
    (Pdb) continue
    <BLANKLINE>


test_pdb failed

== Tests result: FAILURE ==

1 test failed:
    test_pdb

Total duration: 2.8 sec
Tests result: FAILURE