[MERGE] Add exit() on progressbars from TestUIFactory

[Martin Pool]

Martin Pool has voted reject.
Status is now: Vetoed
Comment:
I don't think this solves enough of the issues with progress bars and 
generators, so I'm going to withdraw the patch.  My current thinking is 
that code outside the generator should report on progress, though I need 
to look at more cases to see if this is actually enough.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C20090313071327.8539A8148A%40lithe.sourcefrog.net%3E
Project: Bazaar