'An existing policy can be modified only if one of the following is
true:
the policy\'s tenant is the context\'s tenant
the policy is shared with the tenant
Using is_accessible expresses these conditions.'

def _check_policy_change_permission(self, context, old_policy):

    if (not policy_object.QosPolicy.is_accessible(context, old_policy)):
        raise n_exc.PolicyRemoveAuthorizationError(policy_id=old_policy.id)
