The original commit had an unreliable policy info (the peer PPA group), as
correct updating of friends' excuses depends on the processing order.
- Also add the currently investigated package to the policy info.
- Add a HTML excuse too, so that excuses.html actually shows the reason for
blocking.
- Don't invalidate other excuses multiple times.
- Change the policy_info to always carry the friend information with it, as
that's useful to know for accepted packages too. Adjust test_approve_ppa()
accordingly.
- Verify "reason" field in test_sourceppa_policy()
- Add another integration test to ensure that this also applies to unbuilt
packages, not just to rejection from other Policies.
- Avoid FileNotFoundError, this does not yet exist in Python 3.2.
