Cinder volume type delete return none informative error

[Tzach Shefi]

Description of problem:
Currently when you try to delete a volume type (which is in use) Horizon returns -> Error: Unable to delete volume type: ssd

Notice on cinder api.log we get a better explanation-> "deletion failed, VolumeType in use.

Improving Horizon's none informative error would be helpful.

Version-Release number of selected component (if applicable):
RHEL7
openstack-dashboard-2014.1-7.el7ost.noarch

How reproducible:
Every time

Steps to Reproduce:
1. Create volume type
2. Create a new volume, from volume type created above.
3. On admin page, try to delete volume type (it should fail) but notice error message.
4. grep -ir error /var/log/cinder/api.log -> will show cinder's better error notice.

Actual results:
Horizon returns -> Error: Unable to delete volume type: ssd
None informative error.

Expected results:
Should return -> Error: Unable to delete volume type while it's still in use, volume type: ssd.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/105181

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matthias Runge (<email address hidden>) on branch: master
Review: https://review.openstack.org/105181
Reason: no movement for 8 months here

[Matthias Runge (mrunge)]

unassigning here, since there was not change within 8 months

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/213709

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/213709
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=dfeb362b95f2b481ff3231b4821d4a5e94fa2e89
Submitter: Jenkins
Branch: master

commit dfeb362b95f2b481ff3231b4821d4a5e94fa2e89
Author: Masco Kaliyamoorthy <email address hidden>
Date: Mon Aug 17 19:12:23 2015 +0530

    Adding informative message when deleting a used volume type

    Currently when you try to delete a volume type (which is in use) Horizon
    returns a generic message.

    This patch includes in this message the text from the exception, resulting on
    the following message:
    'Error: Volume type '<vol_type>' is still in use.'

    Change-Id: I9577127909dca70a4c45129bf5df7e11b6ab1c2f
    Closes-bug: #1334523