docs: def wait_for_servers(session, servers):
      """Wait for the servers to be ready.
  
      Note(msimonin): we don't garantee the SSH connection to be ready.
      """
      nclient = nova.Client(NOVA_VERSION, session=session,
                            region_name=os.environ['OS_REGION_NAME'])
      while True:
          deployed = []
          undeployed = []
          for server in servers:
              c = nclient.servers.get(server.id)
              if c.addresses != {} and c.status == 'ACTIVE':
                  deployed.append(server)
              if c.status == 'ERROR':
                  undeployed.append(server)
          logger.info("[nova]: Polling the Deployment")
          logger.info("[nova]: %s deployed servers" % len(deployed))
          logger.info("[nova]: %s undeployed servers" % len(undeployed))
          if len(deployed) + len(undeployed) >= len(servers):
              break
          time.sleep(3)
      return deployed, undeployed