def gen_delta_msg(total_changes):
    """Return string of changes for the PR message."""
    delta = "Changes:\n"
    delta += "========\n"
    for distro in sorted(total_changes):
        if not total_changes[distro]:
            continue
        delta += "%s Changes:\n" % distro.title()
        delta += "---------------\n"
        for d in sorted(total_changes[distro]):
            delta += '* {0}\n'.format(d)
        delta += "\n"
    return delta