Errors ignore output string type

[mbaum0]

If a configuration is missing 'apiversion', 'type', etc, keys, kubeval dumps the issue to log.Error, prints null, and exits.
When the -o flag is specified as json, I would expect kueval to report the error in json format.

Example

# test.yaml

apiVersion: apps/v1
#kind: Deployment
metadata:
  name: sandbox
spec:
  replicas: astring
  selector:
    matchLabels:
      app: sandbox
  template:
    metadata:
      labels:
        app: moda-sandbox
    spec:
      dnsPolicy: Default
      containers:
      - name: sandbox
        image: sandbox
        ports:
        - name: http
          containerPort: 8080
          protocol: TCP
        envFrom:
          - configMapRef:
              name: kube-cluster-metadata

Current output:

$ ./bin/kubeval -d test.yaml -o json
ERR  - test.yaml: Missing 'kind' key
null

Possible JSON output:

$ ./bin/kubeval -d test.yaml -o json
[
        {
                "filename": "test.yaml",
                "kind": "Deployment",
                "status": "invalid",
                "errors": [
                        "spec.replicas: Missing 'kind' key"
                ]
        }
]

[mbaum0]

It looks like if apiversion or type aren't specified, it isn't possible to build the URL to download the appropriate schema. So kubeval fails fast and makes these checks before even testing against the schema