Make sure we print exception stack on all test failures.
Make sure we print exception stack on all test failures.

* subversion/tests/cmdline/svntest/main.py
  (_log_exception): Don't require a message.
  (TestRunner.run): Log the exception stack on a generic failure.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion