config: Add the foundation for GDPR privacy configuration

See #4616

hugolib/hugo_sites_build.go

@@ -168,7 +168,9 @@ func (h *HugoSites) assemble(config *BuildCfg) error {
 	if len(h.Sites) > 1 {
 		// The first is initialized during process; initialize the rest
 		for _, site := range h.Sites[1:] {
-			site.initializeSiteInfo()
+			if err := site.initializeSiteInfo(); err != nil {
+				return err
+			}
 		}
 	}