Code review comment for ~pfsmorigo/ubuntu-cve-tracker:usn_pocket

I have gone ahead and merge this proposal after:

  - rebasing against origin/master,
  - dropping the commit that made the no longer needed change for the HIDDEN prompt
  - added a couple of commits that expanded the json slightly, so that at the lowest level it's a dict rather than a list (so we don't have to rmember that version is position 0, etc) as well as including an 'origin' field which records which ppa(s) sis-changes collectied information against. This can be used as part of the heuristic for determining what the pocket should be.
  - fixed a couple of bugs for things like source packages that only produce a binary for one architecture (and not the 'all' architecture), as well as changes files that contain descriptions for phantom binary packages.

The necessary changes to lp:usn-tool/usn.py have already landed.

This should not break USN publication, but if it does, a revert can be done via:

  git revert -s -m 1 9879c82bc7902e287d17cb3840b370497a887cba

If done correctly, it should auto-generate a commit message like:

  This reverts commit 9879c82bc7902e287d17cb3840b370497a887cba, reversing
  changes made to 36ea6d05426692b92ed4dacd346a45cc0de01e6a.

Thanks!