cbbackupmgr error message is not clear about rbac

Install Couchbase Server 5.0.0-3497 on 4 centos 7.x servers
Create a default bucket and load 1000 docs.
Create a user rbacuser with roles views_admin[*] that does not have permission to do backup
Run cbbackupmgr with rbacuser.
Backup failed as expected but error message does not mention it's permission issue.
Error message: "Error backing up cluster: Unable to find the latest vbucket sequence numbers. This might be due to a node in the cluster being unreachable"

/opt/couchbase/bin//cbbackupmgr backup --archive /tmp/entbackup --repo backup --cluster http://172.23.121.224:8091 --username rbacbackup --password password  --no-progress-bar

2017-08-21 23:25:21,088 - root - INFO - command executed successfully

2017-08-21 23:25:21,088 - root - INFO - Error backing up cluster: Unable to find the latest vbucket sequence numbers. This might be due to a node in the cluster being unreachable.

Build with error message "Error backing up cluster: Invalid permissions" is 5.0.0-3456