adding trace of the orignal error

Author: Andrei Neagu

packages/service-library/src/servicelib/long_running_tasks/errors.py

@@ -36,7 +36,9 @@ class TaskExceptionError(BaseLongRunningError):
 
 class TaskRaisedUnserializableError(BaseLongRunningError):
     msg_template: str = (
-        "Task {task_id} finished with an unserializable exception: '{exception}'"
+        "Task {task_id} raised an exception that could not be serialized.\n"
+        "Original exception: '{original_exception_str}'\n"
+        "As a consequence, the following error was raised: '{exception}'"
     )
 
 

packages/service-library/src/servicelib/long_running_tasks/task.py

@@ -364,7 +364,9 @@ async def _tasks_monitor(self) -> None:
                         result_field = ResultField(
                             str_error=dumps(
                                 TaskRaisedUnserializableError(
-                                    task_id=task_id, exception=serialization_error
+                                    task_id=task_id,
+                                    exception=serialization_error,
+                                    original_exception_str=f"{e}",
                                 )
                             )
                         )