Fix error handling in test_harness.py
Fix error handling in test_harness.py

If this was run under python3 and a compilation error occurred,
it would throw another exception while trying to report the error.

[ci skip]

jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor