creating a net association twice results in a internal error

[Mathieu Rohon]

running the following command twice result in an internal server error after the second command :

#neutron bgpvpn-net-assoc-create --network 'net-id' 'bgpvpn-id'

The expected behavior would be not to create a new entry but return the existing one

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/252948

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/252948
Committed: https://git.openstack.org/cgit/openstack/networking-bgpvpn/commit/?id=bd6471dbbc61fc30eac91d86b6908724179b48b3
Submitter: Jenkins
Branch: master

commit bd6471dbbc61fc30eac91d86b6908724179b48b3
Author: Mathieu Rohon <email address hidden>
Date: Thu Dec 3 13:19:18 2015 +0000

    Raise an exception for identical associations

    When a request asks for creating a network association that
    already exists, we have to catch the DB exception and raise an
    exception that respond an error code 400.

    Change-Id: Iafcaa6b016bc5f39f5ee1d64ef7ff627efa74183
    Closes-Bug: 1512714