Creates a distributed virtual portgroup on a distributed virtual switch
    (dvs)

    dvs_ref
        The dvs reference

    spec
        Portgroup spec (vim.DVPortgroupConfigSpec)

def create_dvportgroup(dvs_ref, spec):
    '''
    Creates a distributed virtual portgroup on a distributed virtual switch
    (dvs)

    dvs_ref
        The dvs reference

    spec
        Portgroup spec (vim.DVPortgroupConfigSpec)
    '''
    dvs_name = get_managed_object_name(dvs_ref)
    log.trace('Adding portgroup %s to dvs \'%s\'', spec.name, dvs_name)
    log.trace('spec = %s', spec)
    try:
        task = dvs_ref.CreateDVPortgroup_Task(spec)
    except vim.fault.NoPermission as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(
            'Not enough permissions. Required privilege: '
            '{0}'.format(exc.privilegeId))
    except vim.fault.VimFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(exc.msg)
    except vmodl.RuntimeFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareRuntimeError(exc.msg)
    wait_for_task(task, dvs_name, six.text_type(task.__class__))