Return the contents of the buckets cache file

def _read_buckets_cache_file(cache_file):
    '''
    Return the contents of the buckets cache file
    '''

    log.debug('Reading buckets cache file')

    with salt.utils.files.fopen(cache_file, 'rb') as fp_:
        try:
            data = pickle.load(fp_)
        except (pickle.UnpicklingError, AttributeError, EOFError, ImportError,
                IndexError, KeyError):
            data = None

    return data