* catch specific errors rather than bare exceptions * for example [these 3](https://github.com/pysal/access/blob/29b043610c366873d4762b9a64aede2b24cfa0bb/access/raam.py#L181-L204) for declaring `travel_np`, `supply_np`, and `demand_np` – kind of error is expected to be raised here? * `AttributeError`, `ValueError`, something else? * xref #65