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
