error if checked program calls quit()

[stgm]

This code:

if __name__ == '__main__':
    time = str(input("Hoe laat is het? "))
    if meal(time) == 'ontbijt':
        x = 'ontbijt'
    elif meal(time) == 'lunch':
        x = 'lunch'
    elif meal(time) == 'avondeten':
        x = 'avondeten'
    elif meal(time) == None:
        quit(1)
    print(f"het is tijd voor {x}")

yields ExitError -> exit(1) while trying to import the code as a check result.
I think this is expected behaviour from CheckPy.

The phrase while trying to import the code is somewhat misleading for students; it is clearly running the code as main or it would not have reached the quit() call. Would be good if the error correctly reports this context.

---

Now, when doing quit() without an exit code, which was actually what this student submitted, the CheckPy code crashes internally:

  File "checkpy/lib/basic.py", line 205, in _getModuleAndOutputOf
    message = "exit({}) while trying to import the code".format(int(e.args[0])),
                                                                ~~~^^^^^^^^^^^
TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType'

Would be nice if it handles quit() without an exit code, too.