raise exception if sliver's slice has no subnet
raise exception if sliver's slice has no subnet

cboling/xos,cboling/xos,opencord/xos,open-cloud/xos,wathsalav/xos,jermowery/xos,xmaruto/mcord,open-cloud/xos,cboling/xos,zdw/xos,xmaruto/mcord,wathsalav/xos,cboling/xos,wathsalav/xos,opencord/xos,cboling/xos,zdw/xos,open-cloud/xos,zdw/xos,wathsalav/xos,xmaruto/mcord,jermowery/xos,jermowery/xos,xmaruto/mcord,jermowery/xos,opencord/xos,zdw/xos