improve diagnostic

python/test_trace_generator_manager.py

@@ -169,7 +169,7 @@ class TestTraceGeneratorManager():
             for _stream_name, line in list(self._queue.queue):
                 if line[:14] == "*** error: at ":
                     # error
-                    raise RuntimeError("bad: %s"%line[:14])
+                    raise RuntimeError("bad: %s"%line)
 
             self._manage_bad_return_code()