fixes 1033849 - debug persona login

@rhelmer (cc @AdrianGaudebert) r?

It's not pretty but it's potentially super useful to people struggling with login.
![screenshot 2014-07-02 16 59 42](https://cloud.githubusercontent.com/assets/26739/3464040/006594b0-0245-11e4-8da6-43c99fe00b2c.png)

Why not? Ultimately it was quite a lazy thing to do. I just didn't want to have to defined two more entries in urls.py and two more view functions. Keeping it all in one view function is kinda neat. And the perfection of this view function isn't important since it's not an operational thing.