Since you have already checked the replication I would suggest you to ignore as this is a warning message seen in 6.7u3b.
Just close the dialogue box and proceed with the upgrade. Please make sure that you have powered off snapshots of all the nodes before upgrade.
Thanks Nirmal, I probably will. I found the logfile about the error in the bundle -
vmafdupgrade.replicationValidator Running: ['/usr/lib/vmware-vmdir/bin/vdcrepadmin', '-f', 'showservers', '-h', 'localhost', '-u',
and then after the -u, it just has jibberish. I guess it's supposed to be an encrypted credential, but doesn't seem to appear formatted like an encrypted credential
ERROR vmafdupgrade.replicationValidator Unable to retrieve VMDir servers
ERROR vmafdupgrade.replicationValidator Stdout: Vdcrepadmin failed. Error [User invalid credential] 
But as I mentioned, manually checking with vdcrepadmin with a known good password indicates all is well.
You are correct. This happened because of the same where the script generates the errors and we are seeing this specially with 6.7u3b.
We even see this on embedded standalone VCSA as well.
Hope you were able to complete the upgrade.
The upgrade went without issue. thanks!