def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def test_invalid_isointerval_error():
    try:
        inputs.iso8601interval('2013-01-01/blah')
    except ValueError as error:
        assert_equal(
            str(error),
            "Invalid argument: 2013-01-01/blah. argument must be a valid ISO8601 "
            "date/time interval.",
        )
        return
    assert False, 'Should raise a ValueError'