Stack trace still has too many levels of stack

[Jonathan Lange]

Running Version: 0.9.11+bzr230~ppa33~oneiric1.

======================================================================
FAIL: tests.test_symbolfile.TestSymbolFileParsing.test_dodgy
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jml/src/pkgme-binary/symbol-database/devportalbinary/tests/test_symbolfile.py", line 23, in test_dodgy
    self.assertRaises(ValueError, SymbolFile.parse, symbol_contents)
  File "/home/jml/src/testtools/trunk/testtools/testcase.py", line 388, in assertRaises
    self.assertThat(lambda: callableObj(*args, **kwargs), matcher)
  File "/home/jml/src/testtools/trunk/testtools/testcase.py", line 411, in assertThat
    raise MismatchError(matchee, matcher, mismatch, verbose)
MismatchError: <function <lambda> at 0x1487488> returned <devportalbinary.symbolfile.SymbolFile object at 0x148a390>
id=26, tests=45, failures=8

Only the top-most level should be present in the error message.

[Jonathan Lange (jml)]

Turns out this is because of this code in Python's unittest:

        if exctype is test.failureException:

And because we are raising MismatchErrors for most of our asserts.