I've installed devstack on a VM on my laptop, and at first I was able to log in to the Horizon dashboard. But I stopped my VM and restarted it later, now when I log in the authentication fails. My horizon_error.log shows the following: DEBUG:openstack_auth.backend:Authorization Failed: HTTPConnectionPool(host='127.0.0.1', port=5000): Max retries exceeded with url: /v2.0/tokens (Caused by <class 'socket.error'>: [Errno 111] Connection refused).

I think Keystone isn't running. How do I tell if it is, and how do I start it if it isn't? If it is running, then what could be going wrong here?