Shouldn't this be True? Like above at line 61. And note below at line 88/89, the "enable tracemalloc" message is appended if tracing is false.

I thought that except Exception was added because the tracemalloc module was optional. In that case it is reasonable that we should not suggest to use the tracemalloc module.

But in fact, it most likely fails because the import system is already broken at Python shutdown, so no new modules can be imported. And if we are in the else block, then either the import system works, or tracemalloc was imported earlier. Can we suggest to enable it? Who knows. I initially thought that we can, running Python with -X tracemalloc seems worked in these examples. But I failed to write tests that do not involve running tests via unittest (or even libregrtest), so I am now not sure that it always works. So perhaps it is safer to set tracing = True here.

The tracing variable is a bit of a misnomer -- it's just used to suppress the "Enable tracemalloc" message. Maybe reverse the sense and rename it to "suggest_tracemalloc"? Then we'd get

# If we're already tracing, don't suggest to enable tracemalloc
suggest_tracemalloc = not tracemalloc.is_tracing()

The idea being that if we're already tracing the suggestion is redundant. (See the original PR gh-10486 where it was introduced.)