RuntimeError: generator raised StopIteration

[wushuo1997]

I am running main.py on pycharm after I set 'n_worker_preprocessing':2,'use_exsiting_preprocessing':1
in config_submit.py

However it keeps report the runtime error above.
I think there must be sth wrong with the setting of 'use_exsiting_preprocessing':1
since the interpreter reports:

Traceback (most recent call last):
File "/Users/wushuo/Documents/DSB2017-master/main.py", line 26, in
use_existing=config_submit['use_exsiting_preprocessing'])
File "/Users/wushuo/Documents/DSB2017-master/preprocessing/full_prep.py", line 125, in full_prep
_=pool.map(partial_savenpy,range(N))
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/multiprocessing/pool.py", line 268, in map
return self._map_async(func, iterable, mapstar, chunksize).get()
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/multiprocessing/pool.py", line 657, in get
raise self._value
RuntimeError: generator raised StopIteration

could anyone help me?I'm in a hurry now.

thank you very much in advance!!