String type instead of error type and changelog.

.changelog/10612.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+acl: replication routine to report the last error message.
+```

agent/consul/acl_replication.go

@@ -484,12 +484,12 @@ func (s *Server) IsACLReplicationEnabled() bool {
 		s.config.ACLTokenReplication
 }
 
-func (s *Server) updateACLReplicationStatusError(errorMsg error) {
+func (s *Server) updateACLReplicationStatusError(errorMsg string) {
 	s.aclReplicationStatusLock.Lock()
 	defer s.aclReplicationStatusLock.Unlock()
 
 	s.aclReplicationStatus.LastError = time.Now().Round(time.Second).UTC()
-	s.aclReplicationStatus.LastErrorMessage = errorMsg.Error()
+	s.aclReplicationStatus.LastErrorMessage = errorMsg
 }
 
 func (s *Server) updateACLReplicationStatusIndex(replicationType structs.ACLReplicationType, index uint64) {

agent/consul/leader.go

@@ -810,7 +810,7 @@ func (s *Server) runLegacyACLReplication(ctx context.Context) error {
 				0,
 			)
 			lastRemoteIndex = 0
-			s.updateACLReplicationStatusError(err)
+			s.updateACLReplicationStatusError(err.Error())
 			legacyACLLogger.Warn("Legacy ACL replication error (will retry if still leader)", "error", err)
 		} else {
 			metrics.SetGauge([]string{"leader", "replication", "acl-legacy", "status"},
@@ -927,7 +927,7 @@ func (s *Server) runACLReplicator(
 				0,
 			)
 			lastRemoteIndex = 0
-			s.updateACLReplicationStatusError(err)
+			s.updateACLReplicationStatusError(err.Error())
 			logger.Warn("ACL replication error (will retry if still leader)",
 				"error", err,
 			)

api/acl.go

@@ -97,6 +97,7 @@ type ACLReplicationStatus struct {
 	ReplicatedTokenIndex uint64
 	LastSuccess          time.Time
 	LastError            time.Time
+	LastErrorMessage     string
 }
 
 // ACLServiceIdentity represents a high-level grant of all necessary privileges