Why does this hang the system up

[Able98]

If I hit control C multiple times it will finally stop the program. It just takes a while.
Since I now have access to the terminal output I can see there are multiple exception messages.
Perhaps ten or more I think coming from LIB functions and not my code.
Here is a typical example:

multiprocessing.pool.RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/joblib/_parallel_backends.py", line 350, in __call__
    return self.func(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/joblib/parallel.py", line 131, in __call__
    return [func(*args, **kwargs) for func, args, kwargs in self.items]
  File "/usr/local/lib/python3.5/dist-packages/joblib/parallel.py", line 131, in <listcomp>
    return [func(*args, **kwargs) for func, args, kwargs in self.items]
  File "pyethrecover3.py", line 79, in attempt
    raise PasswordFoundException("Password Found")
PasswordFoundException: Password Found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.5/multiprocessing/pool.py", line 119, in worker
    result = (True, func(*args, **kwds))
  File "/usr/local/lib/python3.5/dist-packages/joblib/_parallel_backends.py", line 359, in __call__
    raise TransportableException(text, e_type)
joblib.my_exceptions.TransportableException: TransportableException
___________________________________________________________________________
PasswordFoundException                             Thu Jun  8 07:14:19 2017
PID: 2409                                    Python 3.5.2: /usr/bin/python3

I suspect that one of the problems may be that the exception is raised from inside a for loop and the loop has to be stopped first. I know that in a Windows program using C# trying to exit a program from inside a loop will cause similar problems.

Here is the loop:

Parallel(n_jobs=-1)(delayed(attempt)(w, pw) for pw in pwds)

It seems to be a combo statement and could it be broken down into separate statements so I will understand it better. I know so little about python syntax.