The current build (160016) is expiring in about 14 hours. Unfortunately, I'm running into some issues (again), trying to upload a new build – iTunes Connect (TestFlight) is complaining about supposedly missing code signatures, even though pretty much the same setup worked fine last time. I have a couple of ideas for working around this, but I'm not sure if they'll pan out, so I would strongly recommend that you make a backup of your files now, if you're in the beta, because it's more difficult to do this after the beta has expired. Here's a simple backup script if you need it: http://bit.ly/pythonistabackup
It looks like something has changed on Apple's (server) side. The problem seems similar to the one I had two(?) months ago, but I thought I had figured that out. The error message is less detailed this time, so I'm not quite sure what the exact problem is, and how to get around it. I'll keep you posted.