nbrun needs to handle exceptions that are meant to happen

[rgommers]

Failure when running tests/nbrun.py locally:

eventsDS = xnd.xnd(data, type="20 * {id: int64, device: string}")
------------------

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-1f72a7c7018c> in <module>
----> 1 eventsDS = xnd.xnd(data, type="20 * {id: int64, device: string}")

~/anaconda3/envs/xnd/lib/python3.7/site-packages/xnd/__init__.py in __new__(cls, value, type, dtype, levels, typedef, dtypedef, device)
    131             device = (name, no)
    132 
--> 133         return super().__new__(cls, type=type, value=value, device=device)
    134 
    135     def __repr__(self):

TypeError: xnd: expected dict, not 'tuple'
TypeError: xnd: expected dict, not 'tuple'

That TypeError is part of the story of the notebook, it's demonstrating an expected error. So nbrun should be updated to handle it.