I've got a memory issue in my modified Python interpreter I'm trying to debug. Output at the end of the problematic unit test looks like this:

== Tests result: FAILURE then SUCCESS ==

1 test OK.

1 re-run test:

Total duration: 2.9 sec
Tests result: FAILURE then SUCCESS
Debug memory block at address p=0x55a227969080: API ''
    0 bytes originally requested
    The 7 pad bytes at p-7 are not all FORBIDDENBYTE (0xfd):
        at p-7: 0x00 *** OUCH
        at p-6: 0x00 *** OUCH
        at p-5: 0x00 *** OUCH
        at p-4: 0x00 *** OUCH
        at p-3: 0x00 *** OUCH
        at p-2: 0x00 *** OUCH
        at p-1: 0x00 *** OUCH
    Because memory is corrupted at the start, the count of bytes requested
       may be bogus, and checking the trailing pad bytes may segfault.
    The 8 pad bytes at tail=0x55a227969080 are not all FORBIDDENBYTE (0xfd):
        at tail+0: 0x00 *** OUCH
        at tail+1: 0x00 *** OUCH
        at tail+2: 0x00 *** OUCH
        at tail+3: 0x00 *** OUCH
        at tail+4: 0x00 *** OUCH
        at tail+5: 0x00 *** OUCH
        at tail+6: 0x00 *** OUCH
        at tail+7: 0x00 *** OUCH
    The block was made by call #0 to debug malloc/realloc.

Enable tracemalloc to get the memory block allocation traceback

Looking at the tracemalloc module docs and trying various command line args (-X tracemalloc=5) or environment variables (PYTHONTRACEMALLOC=5) I'm unable to provoke any different output. The module docs give a tantalizing suggestion:

Example of output of the Python test suite:

but I see no command line args related to running the test suite with tracemalloc enabled.

Pointers appreciated.