BUG: pd.Timedelta np.int, np.float. fixes #8757

closes #8757 
hm, actually, no. ``np.issubdtype`` chokes on anything that's not a dtype, so I don't think that the additional error text is reachable. Two potential options:

1. Remove my changes to the error reporting and let the numpy error reach the user.
2. Move the ``kwargs = dict()`` line inside the try block and test for numpy's ``TypeError: data type "foo" not understood`` in the except block.

I'd go for the first option.