Support dependent changes to import neutron-lib
Support dependent changes to import neutron-lib

Make changes for importing neutron-lib to reuse NeutronException
in the patch set https://review.openstack.org/#/c/256355/.

Co-Authored-By: Mohankumar <6bc7b7019c2f88e6771d11c585064700b09cab62@huawei.com>
Change-Id: I124646a8f8cd190272a5d4afa3c8a0925bb444e2

openstack/neutron-classifier,openstack/neutron-classifier