6.5 - Replication Controller Specifications

As I tried to create the replicationController, kubectl returned an error with the following message:

The ReplicationController "redis" is invalid: spec.template.metadata.labels: Invalid value: null: `selector` does not match template `labels`

As soon as I added the `labels` definition in the template to make sure the `app: redis` label is applied ie the new pod created by the ReplicationController. Indeed, when I looked at the documentation of the Pod Template section of the Replication Controller (https://kubernetes.io/docs/user-guide/replication-controller/#pod-template), I read:  In addition to required fields for a Pod, a pod template in a ReplicationController must specify appropriate labels.

After updating my yaml definition to add this labels tempalte for new pods, I'm able to create the replicationController. 

Should this line by added to the sample in the slides, or did I missed anything which makes this extra line optional?

My new yaml is therefore: (the spec/template/metadata/labels/ node has been added)

apiVersion: v1
kind: ReplicationController
metadata:
  name: redis
namespace: default
spec:
  replicas: 2
selector:
    app: redis
template:
    metadata:
      name: redis
labels:        # This line is not in the 6.5 slides
        app: redis   # This line is not in the 6.5 slides
    spec:
      containers:
        - image: redis:3.2
imagePullPolicy: IfNotPresent
name: redis