Treat JUnit errors as failures to increase visibility

[tlk]

Before this change cd app; ant test would return "BUILD SUCCESS"
even when unit tests were returning errors.

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully ran tests with your changes

Please note: this change will make (already) failing tests break the "ant test" target.

[tlk]

This is related to #9697 (Arduino IDE CI)

[cmaglie]

Ok now I see it, I guess this answer my question #9696 (comment)