Serialization of exotic functions fails on Windows

[krzysztofarendt]

The following unit test fails on Windows:

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ERROR: test_exotic_pickling (__main__.TestModestga)
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Traceback (most recent call last):
  File "modestga\test\test.py", line 233, in test_exotic_pickling
    workers=2)
  File "d:\code\modestga\modestga\ga.py", line 167, in minimize
    p.start()
  File "D:\Anaconda3\envs\modestga\lib\multiprocessing\process.py", line 112, in start
    self._popen = self._Popen(self)
  File "D:\Anaconda3\envs\modestga\lib\multiprocessing\context.py", line 223, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "D:\Anaconda3\envs\modestga\lib\multiprocessing\context.py", line 322, in _Popen
    return Popen(process_obj)
  File "D:\Anaconda3\envs\modestga\lib\multiprocessing\popen_spawn_win32.py", line 89, in __init__
    reduction.dump(process_obj, to_child)
  File "D:\Anaconda3\envs\modestga\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
AttributeError: Can't pickle local object 'TestModestga.test_exotic_pickling.<locals>.FunWrapper'

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On Linux it works fine.