Prevent SystemExits when running tests

Adds a check for SystemExit exceptions during tests
to convert them into a test failure rather than an exit.
Includes the traceback in the failure so the source of
the exit can be located.

Related-Bug: #1364171
Change-Id: I2c7d9010ebf935d39ed58fe7a6fc4a1a867e2548
Merge "Prevent SystemExits when running tests"