Description of problem:


Version-Release number of selected component (if applicable):


How reproducible:

100%

Steps to Reproduce:
1. install the latest undercloud, including tuskar
2. run the following line twice: #tuskar plan-create -d 'just a test' test1
3.

Actual results:
you would get a dirty traceback

Expected results:
a meaning message is being shown to the user, without any traceback

Additional info:
the traceback:

$ tuskar plan-create -d 'just a test' test1
ERROR (shell) Exiting due to an error:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/tuskarclient/shell.py", line 245, in main
    TuskarShell(sys.argv[1:]).run()
  File "/usr/lib/python2.7/site-packages/tuskarclient/shell.py", line 75, in run
    args.func(tuskar_client, args)
  File "/usr/lib/python2.7/site-packages/tuskarclient/v2/plans_shell.py", line 116, in do_plan_create
    description=vars(args).get('description')
  File "/usr/lib/python2.7/site-packages/tuskarclient/v2/plans.py", line 97, in create
    return self._post(self._path(), fields)
  File "/usr/lib/python2.7/site-packages/tuskarclient/openstack/common/apiclient/base.py", line 178, in _post
    body = self.client.post(url, json=json).json()
  File "/usr/lib/python2.7/site-packages/tuskarclient/openstack/common/apiclient/client.py", line 358, in post
    return self.client_request("POST", url, **kwargs)
  File "/usr/lib/python2.7/site-packages/tuskarclient/openstack/common/apiclient/client.py", line 345, in client_request
    self, method, url, **kwargs)
  File "/usr/lib/python2.7/site-packages/tuskarclient/openstack/common/apiclient/client.py", line 261, in client_request
    method, self.concat_url(endpoint, url), **kwargs)
  File "/usr/lib/python2.7/site-packages/tuskarclient/openstack/common/apiclient/client.py", line 201, in request
    raise exceptions.from_response(resp, method, url)
Conflict: test1 (HTTP 409)