Fix text-search model unpickling.

[stepan-anokhin]

The Problem

When loading text-search model from winnow/text_search/models/model_best.pth.tar the following error occurs:

Traceback (most recent call last):
  File "/home/stepan/work/benetech/programs/anaconda/envs/winnow/lib/python3.6/site-packages/torch/serialization.py", line 608, in load
    return _legacy_load(opened_file, map_location, pickle_module, **pickle_load_args)
  File "/home/stepan/work/benetech/programs/anaconda/envs/winnow/lib/python3.6/site-packages/torch/serialization.py", line 787, in _legacy_load
    result = unpickler.load()
ModuleNotFoundError: No module named 'configs'

Root Cause

The model is saved using pickle with different import paths (e.g. import configs instead of import winnow.text_search.configs). According to the pickle documentation:

pickle can save and restore class instances transparently, however the class definition must be importable and live in the same module as when the object was stored.

Possible Fix

See the following answer on StackOverflow: https://stackoverflow.com/a/2121918