Fix flakiness

[blazyy]

A test inside test_globals.py was found to be flaky, i.e. test that both pass and fail despite no changes to the code or the tests itself.

Using the pytest-flakefinder plugin, when the tests were re-run more than once, the test test_debug_default_value was failing. Upon looking at the code, the reason was because the value of debug was not being reset back to False on a subsequent run. To fix this, I just added and extra call which initially sets the value of debug to False.

In general, flaky tests are a pain to fix with regards to locating the root of the actual problem, so it's a good idea to fix them when you detect them. I'm aware that the tests might not be re-run at all, but this change makes the entire module more robust and future-proof so it's just a small fix for you to consider.

To reproduce:

Install pytest-flakefinder by following the instructions here.
At root directory, run python3 -m pytest --flake-finder
After implementing the fix, all tests pass successfully, both with and without the pytest-flakefinder plugin being used.