Add test for missing datasource config template

- Add test for `missing_datasource_config.ctp` to be rendered correctly
- Correct displayed message for MissingDriverException by removing `"`(see old result bellow)
![capture d ecran 2014-08-14 21 36 29](https://cloud.githubusercontent.com/assets/4977112/3925701/608ec00c-23ea-11e4-8d99-f0cc2356a583.png)