placement: Inappropriate error message in the input validation in traits API

[Takashi Natsume]

When creating a trait by "PUT /traits/{name}",
If the name of trait exceeds max character length (255 chars),
the following error message is got.
But it is not appropriate.

The trait is invalid. A valid trait must include prefix "CUSTOM_" and use following characters: "A"-"Z", "0"-"9" and "_"

Environment
-----------

nova master(commit b9c35aea70e0b413992cb77bd451691883afa2ef)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/524088

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/pike
Review: https://review.openstack.org/526465

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/524088
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e51a14bc93fc8a0661a3dfab548bad8c19ff2085
Submitter: Zuul
Branch: master

commit e51a14bc93fc8a0661a3dfab548bad8c19ff2085
Author: Takashi NATSUME <email address hidden>
Date: Thu Nov 30 16:19:42 2017 +0900

    [placement] Fix an error message in API validation

    Fix the error message in validation of the following API
    when the name exceeds max character length(255).

    * PUT /traits/{name}

    Change-Id: I2bbbadd7842bf4652d3c32ae3e5c74e2e159990b
    Closes-Bug: #1735343

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/526465
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=fa36ccefd28d13435babc5b5fea428db4d372a7b
Submitter: Zuul
Branch: stable/pike

commit fa36ccefd28d13435babc5b5fea428db4d372a7b
Author: Takashi NATSUME <email address hidden>
Date: Thu Nov 30 16:19:42 2017 +0900

    [placement] Fix an error message in API validation

    Fix the error message in validation of the following API
    when the name exceeds max character length(255).

    * PUT /traits/{name}

    Conflicts:
          nova/tests/functional/api/openstack/placement/gabbits/traits.yaml

    NOTE(mriedem): The conflict is due to not having commit
    f269023c49dcf24fd42a4933fc7d31f3aaa2e64d in Pike.

    Change-Id: I2bbbadd7842bf4652d3c32ae3e5c74e2e159990b
    Closes-Bug: #1735343
    (cherry picked from commit e51a14bc93fc8a0661a3dfab548bad8c19ff2085)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 17.0.0.0b3 development milestone.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 16.1.0 release.