[nailgun] Nailgun doesn't show error details while assigning node roles (virt, compute-vmware, cinder-vmware) with restrictions

[Vitalii Kulanov]

Detailed bug description:
While assigning node roles (virt, compute-vmware, cinder-vmware) for specific cluster nailgun doesn't show detailed restriction description.

[root@fuel ~]# fuel2 env add nodes -e 1 -n 1 -r virt
400 Client Error: Bad Request for url: http://10.20.0.2:8000/api/v1/clusters/1/assignment/ (Role 'virt' restrictions mismatch: )
[root@fuel ~]# fuel2 env add nodes -e 1 -n 1 -r cinder-vmware
400 Client Error: Bad Request for url: http://10.20.0.2:8000/api/v1/clusters/1/assignment/ (Role 'cinder-vmware' restrictions mismatch: )
[root@fuel ~]# fuel2 env add nodes -e 1 -n 1 -r compute-vmware
400 Client Error: Bad Request for url: http://10.20.0.2:8000/api/v1/clusters/1/assignment/ (Role 'compute-vmware' restrictions mismatch: )

Steps to reproduce:
1. Deploy Fuel (e.g. 1 master + 5 nodes).
2. Create new env.
3. Try to assign virt | compute-vmware | cinder-vmware role (python-fuelclient) e.g.:
     fuel2 env add nodes -e 1 -n 1 -r virt
4. The result of command execution:
400 Client Error: Bad Request for url: http://10.20.0.2:8000/api/v1/clusters/1/assignment/ (Role 'virt' restrictions mismatch: )

Expected results:
Detailed restriction mismatch message should be printed

Actual result:
400 Client Error: Bad Request for url: http://10.20.0.2:8000/api/v1/clusters/1/assignment/ (Role 'virt' restrictions mismatch: )

Reproducibility:
Always

Description of the environment:
cat /etc/fuel_build_id:
 262
cat /etc/fuel_build_number:
 262
cat /etc/fuel_release:
 10.0
cat /etc/fuel_openstack_version:
 newton-10.0

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/328830

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/328830
Committed: https://git.openstack.org/cgit/openstack/fuel-web/commit/?id=0855ea37458cefac3e17bba2318785a21da57c2d
Submitter: Jenkins
Branch: master

commit 0855ea37458cefac3e17bba2318785a21da57c2d
Author: tivaliy <email address hidden>
Date: Mon Jun 13 07:08:20 2016 +0300

    Add error message if assign roles with restrictions

    Adds more verbosity to error message of Nailgun response
    during assigning nodes roles with restrictions

    Change-Id: Ibccd0bf0bec2097fdebd08bc4565c06c15d88135
    Closes-Bug: 1591447