mshtml/tests: Better output when an exception is caught.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=8326

Your paranoid android.


=== w2000pro (32 bit) ===
No test summary line found

=== wxppro (32 bit) ===
No test summary line found

=== wvistau64 (32 bit) ===
No test summary line found

=== w2008s64 (32 bit) ===
No test summary line found

=== w7u (32 bit) ===
No test summary line found

=== w8 (32 bit) ===
No test summary line found

=== wvistau64 (64 bit) ===
No test summary line found

=== w2008s64 (64 bit) ===
No test summary line found