It will add a message for each source:

```javascript
"messages": [
  "Fetching cookbook index from https://api.berkshelf.com...",
  "Fetching cookbook index from <internal URL>..."
]
```

Same thing in human:

```text
Fetching cookbook index from https://api.berkshelf.com...
Fetching cookbook index from <internal URL>...
```

We could make this better in another PR, but I think that's "good enough" for now. What do you think?