Extract state reason for failure

builder/amazon/ebs/step_create_ami.go

@@ -54,7 +54,7 @@ func (s *stepCreateAMI) Run(_ context.Context, state multistep.StateBag) multist
 	if _, err := awscommon.WaitForState(&stateChange); err != nil {
 		imagesResp, _ := ec2conn.DescribeImages(&ec2.DescribeImagesInput{ImageIds: []*string{createResp.ImageId}})
 		stateReason := imagesResp.Images[0].StateReason.Message
-		err := fmt.Errorf("Error waiting for AMI: %s. Cause: %s", err, *stateReason)
+		err := fmt.Errorf("Error waiting for AMI: %s. Root cause: %s", err, *stateReason)
 		state.Put("error", err)
 		ui.Error(err.Error())
 		return multistep.ActionHalt