Test error traceback suppressed by default

[hoxu]

Looks like without -v the default is to suppress the traceback of unit test errors:

[INFO]  Executed 1 unit tests
Error:  Test has error: unittest.loader._FailedTest.xxx
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BUILD FAILED - There were 1 error(s) and 0 failure(s) in unit tests (pybuilder/plugins/python/unittest_plugin.py:109)
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I think the default should be to show the traceback that caused the build to fail, regardless of whether -v is used.