Yields 3-tuples of (name, modified, bytes).

def extract_tar(fileobj):
    """Yields 3-tuples of (name, modified, bytes)."""
    import time

    archive = tarfile.open(fileobj=fileobj)
    filenames = [info.name for info in archive.getmembers() if info.isfile()]

    for src_name, dst_name in filter_tzfiles(filenames):
        mtime = archive.getmember(src_name).mtime
        modified = tuple(time.gmtime(mtime)[:6])
        bytes = archive.extractfile(src_name).read()

        yield dst_name, modified, bytes