routing+discovery: uniform error codes in routing

routing/errors.go

@@ -28,6 +28,15 @@ const (
 	// ErrInvalidFundingOutput is returned if the channle funding output
 	// fails validation.
 	ErrInvalidFundingOutput
+
+	// ErrVBarrierShuttingDown signals that the barrier has been requested
+	// to shutdown, and that the caller should not treat the wait condition
+	// as fulfilled.
+	ErrVBarrierShuttingDown
+
+	// ErrParentValidationFailed signals that the validation of a
+	// dependent's parent failed, so the dependent must not be processed.
+	ErrParentValidationFailed
 )
 
 // routerError is a structure that represent the error inside the routing package,