As defined in del_all_vgw_stacks() in vcpe_custom_service.py, openstack command is used to delete vGW stack using command line directly:

    param = ' '.join([k + ' ' + v for k, v in self.vcpecommon.cloud.items()])
    openstackcmd = 'openstack ' + param + ' '

    stacks = os.popen(openstackcmd + 'stack list').read()

This cann't work when the script is tested on a vm which is not the openstack controller. Since openstack controller is very important we usually don't test script on it, so the delete will never happen. Maybe curl method using openstack API could work.