pickle periodic boundary conditions

[lksrmp]

Setting PBC_FOLDING TRUE in .scntl file causes error:

AttributeError: Can't pickle local object 'pbc_folding_parallel.<locals>.wrapper'

Deactivating the folding of atoms back into the unit cell stops producing the error.

[lksrmp]

Problem seems to be related to multiprocessing. See here for ideas for possible solution.