The "Managing Geo-replication" document instructs you to create a key at /var/lib/glusterd/geo-replication/secret.pem and suggests that you should lock down SSH access using the "command" option in authorized_keys. The Testing_Passwordless_SSH check in gverify.sh is at odds with both of these things. It executes ssh without the -i option, requiring you to add an entry to ~/.ssh/config. It also tries to execute echo, which won't work if the "command" option is used. I don't know whether there's an option you could pass to gsyncd that would make it exit successfully. Otherwise you'll need to check for the output from gsyncd instead. Obviously -i is required too.
Please point to the URL of the documentation you referred? is it https://github.com/gluster/glusterfs/blob/release-3.5/doc/admin-guide/en-US/markdown/admin_distributed_geo_rep.md
Close, it was this: https://github.com/gluster/glusterfs/blob/master/doc/admin-guide/en-US/markdown/admin_geo-replication.md But regardless of what the documentation says, I think it is very important to be able to lock down the account through authorized_keys anyway.
This bug is getting closed because the 3.5 is marked End-Of-Life. There will be no further updates to this version. Please open a new bug against a version that still receives bugfixes if you are still facing this issue in a more current release.