def open_unicode_data_file(data_file_name):
    """Opens a Unicode data file.

    Args:
      data_file_name: A string containing the filename of the data file.

    Returns:
      A file handle to the data file.
    """
    filename = path.join(_DATA_DIR_PATH, data_file_name)
    return codecs.open(filename, "r", "utf-8")