When you use `concurrent.futures.ProcessPoolExecutor` and an exception is raised in the created process, it doesn't show you the traceback. This makes debugging very annoying. Example file: #!python import sys import concurrent.futures def f(): # Successful assert: assert True return g() def g(): # Hard-to-find failing assert: assert False if __name__ == '__main__': with concurrent.futures.ProcessPoolExecutor(max_workers=1) as executor: assert isinstance(executor, concurrent.futures.Executor) future = executor.submit(f) future.result() print('Main process finished') If you run this under Windows, you get this: Traceback (most recent call last): File "./bug.py", line 20, in <module> future.result() File "c:\python34\lib\concurrent\futures\_base.py", line 402, in result return self.__get_result() File "c:\python34\lib\concurrent\futures\_base.py", line 354, in __get_result raise self._exception AssertionError This is the traceback of the main process, while we want the traceback of the process that failed.