Improve readability of the log message in case there are multiple output datasets.

To improve readability, change:
![screen shot 2014-11-03 at 3 08 43 pm](https://cloud.githubusercontent.com/assets/5114833/4898145/64211f36-640d-11e4-816b-e0e8455e7e69.png)
to
![screen shot 2014-11-03 at 3 11 45 pm](https://cloud.githubusercontent.com/assets/5114833/4898149/6a106da2-640d-11e4-9773-4291a9bddd77.png)