at least on my Windows, the following code:

import sys
sys.modules = []


- when run interactively, causes weird behavior, e.g. exit() doesn't exit the
  interpreter, and print() doesn't print.
  then, pressing Ctrl+C causes 'Assertion failed: !PyErr_Occurred(), file ..\Objects\call.c, line 803'

- when run as a script, causes PyImport_Cleanup() to raise a negative ref count
  Fatal Python error.

  (this is because PyImport_Cleanup() (in Python/import.c) assumes that
  PyImport_GetModuleDict() returned a dict.)


IIUC, this bug was introduced in https://github.com/python/cpython/pull/1638
(which resolved #28411).