"No valid auth source" doesn't bubble up an error when debug is false

[angstwad]

I was thinking that this might be helpful. I ran into this in prod because of a bad path to the apiKey.properties file. It would be useful if this could be configured to bubble up an exception into the request if this occurs.

Specifically talking about this exception: https://github.com/stormpath/stormpath-sdk-python/blob/master/stormpath/auth.py#L260