Why two exceptions

```
  if (err.name === 'NotAllowedError') {
    console.log('The user agent did not grant permission to access the file.');
  } else if (err.name === 'NotFoundError') {
    console.log('The file was not found in Cross-Origin Storage.');
  }
```

It seems like you would expose slightly less information by using `NotFoundError` for both of these cases.