title: Openstack dashboard gives error "Error: Unable to retrieve usage information"
body: <p>I installed OpenStack on an ec2 instance running Ubuntu 14.04 LTS via <a href="https://github.com/openstack-dev/devstack" rel="nofollow">devstack</a>. When I login into the dashboard I get an error "Error: Unable to retrieve usage information"
  When I installed it and logged in for the first time, everything was working fine. But after I stopped my ec2 instance and restarted, I am facing this problem.
  What might be causing this error?
  I used the stable juno version of devstack.
  And the AMI for my ec2 instance is Ubuntu Server 14.04 LTS (HVM), SSD Volume Type.
  Does restarting the instance might have caused some problem?</p>