Add a function to make it easier to debug a test failure caused by an unexpected stop reason. This is similar to the assertState helper function that I added in D127355.
Before:
self.assertEqual(stop_reason, lldb.eStopReasonInstrumentation) AssertionError: 5 != 10
After:
self.assertStopReason(stop_reason, lldb.eStopReasonInstrumentation) AssertionError: signal (5) != instrumentation (10)