make test runner exit with non-0 return status on exceptions (this shadowed an...

make test runner exit with non-0 return status on exceptions (this shadowed an actual bug in this branch)

runtests.py

@@ -2100,3 +2100,4 @@ if __name__ == '__main__':
         except PendingThreadsError:
             # normal program exit won't kill the threads, do it the hard way here
             flush_and_terminate(1)
+        sys.exit(1)