Packer.io Rackspace UK cloud configuration failure

gistfile1.txt

{
  "builders":
  [
    {
      "type": "openstack",
      "username": "",
      "password": "",
      "provider": "rackspace-uk",
      "region": "LON",
      "ssh_username": "root",
      "image_name": "Staging Web Server",
      "source_image": "f70ed7c7-b42e-4d77-83d8-40fa29825b85",
      "flavor": "5"
    }
  ],
  "provisioners": [{
    "type": "shell",
    "inline": [
      "yum -y update",
      "yum install -y tmux"
    ]
  }]
}


$ packer build -debug staging-web.json
Debug mode enabled. Builds will not be parallelized.
openstack output will be in this color.

Build 'openstack' errored: Expected HTTP response code [200]; got 401 instead

==> Some builds didn't complete successfully and had errors:
--> openstack: Expected HTTP response code [200]; got 401 instead

==> Builds finished but no artifacts were created.