A better update_excuses.html

Hi, I firmly believe that reports must make issues obvious and should offer everything useful for digging in deeper. I don't think update_excuses.html does that: it mostly exposes micro-issues and makes you click several times before getting the information you need. It's britney's output re-form

Analyzing migrations: britney, update_output.txt, chdist, dose-distcheck, apt solver 3

Hi, This is a documentation message rather than a report. Let's face it: I'm at the stage where I barely understand some parts of britney's reports but as everyone knows, this is also the stage where we feel the most confident teaching about things. This is written as a story rather than document