Comment 2 for bug 1823198

Reviewed: https://review.opendev.org/650077
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=ade6c9393632e830c2368825568769853fce3b99
Submitter: Zuul
Branch: master

commit ade6c9393632e830c2368825568769853fce3b99
Author: Matt Riedemann <email address hidden>
Date: Thu Apr 4 13:04:33 2019 -0400

    Handle Invalid exceptions as expected in attach_interface

    The bug prompting this is a tempest test which is requesting
    a port attachment to a server but not specifying a port or
    network to use, so nova-compute looks for a valid network
    and finds there are two and raises NetworkAmbiguous. This
    is treated as a 400 error in the API but because this is a
    synchronous RPC call from nova-api to nova-compute,
    oslo.messaging logs an exception traceback for the unexpected
    error. That traceback is pretty gross in the compute logs for
    something that is a user error and the cloud operator has
    nothing to do to fix it.

    We can handle the traceback by registering our expected
    exceptions for the attach_interface method with oslo.messaging,
    which is what this change does.

    While looking to just add NetworkAmbiguous it became clear that
    lots of different user errors can be raised from this method
    and none of those should result in a traceback, so this change
    just expects Invalid and its subclasses.

    The one exception is InterfaceAttachFailed which is raised when
    something in allocate_port_for_instance or driver.attach_interface
    fails. That is an unexpected situation so the parent class for
    InterfaceAttachFailed is changed from Invalid to NovaException so
    it continues to be traced in the logs as an exception.
    InterfaceAttachFailedNoNetwork is kept as Invalid since it is a
    user error (trying to attach an interface when the user has no
    access to any networks).

    test_tagged_attach_interface_raises is adjusted to show the
    ExpectedException handling for one of the Invalid cases.

    Change-Id: I927ff1d8c8f45405833d6012b7d7af37b98b10a0
    Closes-Bug: #1823198