“Accept” in request header is overwritten by default content type without feedback

[Lin Yang]

When user specify one expected response content type that is not supported, it will be replaced with default type application/json without any feedback. In below case, a unsupported type "text/h323'' is specified, however, it response in application/json as usual.

How to reproduce:
$ curl -i -s -X GET -H "X-Auth-Token:<tokenid>" http://127.0.0.1:8082/v1/environments -H "Accept:text/h323"
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: 20
Date: Fri, 31 Jul 2015 02:55:29 GMT

{"environments": []}

Expected behaviour:
One clear message tells user this type is unsupported.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/207705

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/207711

[OpenStack Infra (hudson-openstack)]

Change abandoned by Lin Yang (<email address hidden>) on branch: master
Review: https://review.openstack.org/207705

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/207711
Committed: https://git.openstack.org/cgit/openstack/murano/commit/?id=0739bd29b9dc10daa2941980191e41086b5c8912
Submitter: Jenkins
Branch: master

commit 0739bd29b9dc10daa2941980191e41086b5c8912
Author: Lin Yang <email address hidden>
Date: Fri Jul 31 12:03:14 2015 +0800

    Warn user about unsupported content type

    1) Raise exception to user when the specified content type is unsupported, instead
    of silently replacing it to default type 'application/json'.
    2) Renamed 'InvalidContentType' exception to more clear name
    'UnsupportedContentType'.

    Change-Id: Id336fc4360f451f3b8febfb453e7d0d119ab9b01
    Closes-Bug: #1480036