Converting a Python 2 berkeley db shelve to a python 3 one.

convert.py

## py3
import shelve
import dbm
import pickle
with dbm.open('source', 'r') as source: # no .db here on purpose.
  with shelve.open('destination.db') as destination:
      for key in source.keys():
        key = key.decode('utf-8')
        value = pickle.loads(source[key])
        print(key, value)
        destination[key] = value