[Imps] Patch to convert test_parser to unittest

[Sam Ruby]

James Graham wrote:
> 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!

What about runtests.py?

- Sam Ruby