[Imps] Patch to convert test_parser to unittest

[James Graham]

Sam Ruby wrote:
> The default message produced by UnitTest.assertEqual includes 
> representations for both the expected and actual parse trees.  If the 
> formatting is an issue, a third parameter can be passed to assertEqual 
> that contains the exact message you would like to be produced in case of 
> failure.

Ah, I had missed that somehow. OK, changes checked in with additional error 
messages. Thanks!

-- 
"Eternity's a terrible thought. I mean, where's it all going to end?"
  -- Tom Stoppard, Rosencrantz and Guildenstern are Dead