Log sample:

```
======================================================================
FAIL: test_up_then_down (test.test_gdb.StackNavigationTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/test_gdb.py", line 782, in test_up_then_down
    self.assertMultilineMatches(bt,
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/test_gdb.py", line 297, in assertMultilineMatches
    self.fail(msg='%r did not match %r' % (actual, pattern))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'Breakpoint 1 at 0x801ff160: file Python/bltinmodule.c, line 1168.\n[Thread debugging using libthread_db enabled]\nUsing host libthread_db library "/lib64/libthread_db.so.1".\n\nBreakpoint 1, builtin_id (self=, v=<_PyRuntime+2184>) at Python/bltinmodule.c:1168\n1168\t{\n#16 Frame 0x3fffdfb1118, for file <string>, line 9, in bar (a=1, b=2, c=3)\n#16 Frame 0x3fffdfb1090, for file <string>, line 6, in foo (a=1, b=2, c=3)\n#16 Frame 0x3fffdfb1020, for file <string>, line 14, in <module> ()\nUnable to find an older python frame\n#4 Frame 0x3fffdfb11a8, for file <string>, line 12, in baz (args=(1, 2, 3))\n' did not match '^.*\n#[0-9]+ Frame 0x-?[0-9a-f]+, for file <string>, line 12, in baz \\(args=\\(1, 2, 3\\)\\)\n#[0-9]+ <built-in method pyobject_fastcall of module object at remote 0x[0-9a-f]+>\n#[0-9]+ Frame 0x-?[0-9a-f]+, for file <string>, line 12, in baz \\(args=\\(1, 2, 3\\)\\)\n$'
----------------------------------------------------------------------
Ran 32 tests in 15.312s
FAILED (failures=53)
test test_gdb failed
1 test failed again:
    test_gdb
```

Full log (too long): https://buildbot.python.org/all/#/builders/179/builds/1769/steps/5/logs/stdio

It started to happen (at least more often - however, I cannot find any older failures at the moment) after this commit: https://github.com/python/cpython/commit/b899126094731bc49fecb61f2c1b7557d74ca839

Build link: https://buildbot.python.org/all/#/builders/402/builds/1744

Latest commits (at this moment):
- Fails: https://github.com/python/cpython/commit/375a56bd4015596c0cf44129c8842a1fe7199785
- Passes: https://github.com/python/cpython/commit/424023efee5b21567b4725015ef143b627112e3c
- Fails: https://github.com/python/cpython/commit/288af845a32fd2a92e3b49738faf8f2de6a7bf7c