bug 892004 - errormill for all exceptions in middleware_app

@rhelmer @AdrianGaudebert r?

I know. I went rogue there for a bit and corrected things out of context. Without the `TRUNCATE os_names CASCADE;` I couldn't get the whole suite to pass. How that slipped past Jenkins I just don't know. I guess it's because we don't run tests repeatedly after having created a blank database. 
Also, I made some pep8 fixes that were burning my retina. 

So, once this lands we'll need get IT to update our middleware.ini with the necessary keys from [stage](https://errormill.mozilla.org/webtools/socorro-stage/) and [prod](https://errormill.mozilla.org/webtools/socorro-prod/). That's why I didn't prefix the commit message with "fixes ".