[MERGE] More robust handling of encoding issues in tests.

[Martin Pool]

Martin Pool has voted resubmit.
Status is now: Resubmit
Comment:
This does not pass its own tests, at least when merged into trunk.  I 
can see how getting clearer messages when unprintable objects are 
compared would be useful but I hit that situation fairly rarely.  So I'm 
going to mark this resubmit for now, and let Martin vG or someone else 
revisit this if they need support for this in the test suite.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C48733815.40704%40gmx.net%3E
Project: Bazaar