Description of problem:
Creating a tenant with an existing name raises None (400) instead of an actual Exception with 409 code.

Version-Release number of selected component (if applicable):
# rpm -qa | grep keystone
python-keystoneclient-0.4.1-3.el6.noarch
openstack-keystone-2014.1-0.3.b2.el6.noarch
python-keystone-2014.1-0.3.b2.el6.noarch

How reproducible:


Steps to Reproduce:
1. keystone tenant-create --name <existing name>

Actual results:
exceptions must be old-style classes or derived from BaseException, not NoneType (HTTP 400)

Expected results:
Conflict occurred attempting to store project. (IntegrityError) (1062, "Duplicate entry 'default-demo' for key 'domain_id'") 'INSERT INTO project (id, name, domain_id, description, enabled, extra) VALUES (%s, %s, %s, %s, %s, %s)' ('fa75b34060e44ba694052512f1f7a0f9', 'demo', 'default', None, 1, '{}') (HTTP 409)

Additional info:
maybe create a nicer looking message?