Example of script.py:
-------------------------
class Bla:
    def __del__(self):
        try:
            import xxxx
        except Exception as exc:
            print("import error: [%s] %r" % (type(exc), exc))

bla = Bla()
-------------------------

Running this example logs a strange error:
-------------------------
$ python3.5 script.py
import error: [<class 'TypeError'>] TypeError("'NoneType' object is not iterable",)
-------------------------

The error comes from importlib._bootstrap._find_spec() which tries to iterator on sys.meta_path, whereas PyImport_Cleanup() was called and this function setted sys.meta_path to None.

Attached patch enhances _find_spec() to handle this case to return None. Error with the patch:
-------------------------
$ python3.5 script.py
import error: [<class 'ImportError'>] ImportError('sys.meta_path is None, Python is likely shutting down',)
-------------------------