Resolve "Internal Changes representation is not working as expected"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Closes #152

nucleus/change.go

@@ -46,6 +46,13 @@ func NewChange(device uuid.UUID, currentState ygot.GoStruct, change ygot.GoStruc
 	c.stateOut = stateOut
 	c.requestState = requestState
 	c.errChan = errChan
+
+	// recieve the errors from a Change and log them
+	go func() {
+		errChan := <-c.errChan
+		log.Error(errChan)
+	}()
+
 	return c
 }
 
@@ -116,6 +123,9 @@ func stateManager(ch *Change, timeout time.Duration) (chan<- ppb.Change_State, <
 	stateIn := make(chan ppb.Change_State)
 	stateOut := make(chan ppb.Change_State)
 	stateRequest := make(chan bool)
+	//A Goroutine, which is called from
+	//principalNetworkDomain.ChangeOND is now the reciever
+	//for errorChan
 	errChan := make(chan error)
 	// create ticker and make it wait for 1 week
 	// workaround for delayed ticker start and ugly housekeeping
@@ -126,17 +136,13 @@ func stateManager(ch *Change, timeout time.Duration) (chan<- ppb.Change_State, <
 		for {
 			select {
 			case <-ticker.C:
-				//TODO: errorChan seems problematic here, since there is no real
-				//      reciever available. therefore currently there will be
-				//      only simple logging.
 				err := ch.callback(ch.intendedState, ch.previousState)
 				if err != nil {
 					state = ppb.Change_INCONSISTENT
 					log.Errorf("change %v timed out", ch.cuid)
-					//errChan <- err
+					errChan <- err
 				}
-				log.Errorf("change %v timed out", ch.cuid)
-				//errChan <- fmt.Errorf("change %v timed out", ch.cuid)
+				errChan <- fmt.Errorf("change %v timed out", ch.cuid)
 			case s := <-stateIn:
 				switch s {
 				case ppb.Change_COMMITTED:
@@ -151,8 +157,8 @@ func stateManager(ch *Change, timeout time.Duration) (chan<- ppb.Change_State, <
 					state = ppb.Change_COMMITTED
 					stateOut <- state
 				case ppb.Change_CONFIRMED:
-					// stop the timer, since the changes are now confirmed and a
-					// rollback is not needed anymore
+					// The change has been confirmed and the timer is stopped,
+					// since a rollback is not necessary anymore.
 					ticker.Stop()
 					state = ppb.Change_CONFIRMED
 					stateOut <- state