Check if the salt master has a valid and
    routable IPv6 address available

def _master_supports_ipv6():
    '''
    Check if the salt master has a valid and
    routable IPv6 address available
    '''
    master_fqdn = salt.utils.network.get_fqhostname()
    pillar_util = salt.utils.master.MasterPillarUtil(master_fqdn,
                                                     tgt_type='glob',
                                                     use_cached_grains=False,
                                                     grains_fallback=False,
                                                     opts=__opts__)
    grains_data = pillar_util.get_minion_grains()
    ipv6_addresses = grains_data[master_fqdn]['ipv6']
    for address in ipv6_addresses:
        if _valid_ip6(address):
            return True
    return False