Initialize the local dictionnaries cache in ~/.crosswords/dicts.

def init_storage():
    """
    Initialize the local dictionnaries cache in ~/.crosswords/dicts.
    """
    # http://stackoverflow.com/a/600612/735926
    try:
        os.makedirs(DICTS_PATH)
    except OSError as ex:
        if ex.errno != errno.EEXIST or not os.path.isdir(DICTS_PATH):
            raise