I've recently upgraded my vCenter Server 7.0.3 to 8.0 and during the process I've encountered the following error: Error in method invocation [Errno 1] Unknown host
The error is related to using IP address instead of FQDN as shown in the image below . It will appear in stage 2, after VCSA VM is deployed in the environment.
To avoid it, just use FQDN everywhere. This error was first mentioned on upgrades from 6.7 to 7.0, but somehow in my lab got ported to upgrade from 7.0 to 8.0.