Source Unreadable in Generated File Warning

The path to `source` is given as `[object Object]` in the Generated File warning. Here is an example from the [can-stache docs](http://canjs.github.io/canjs/doc/can-stache.html):

```
    THIS IS A GENERATED FILE -- ANY CHANGES MADE WILL BE OVERWRITTEN

    INSTEAD CHANGE:
    source: [object Object]
    @module can-stache
```
