showing the error message inside pre tag in order to properly render the new lines

New lines are not properly displayed inside the error page. For example, MVC shows the list of scanned view locations when it cannot find the view to render:

![image](https://cloud.githubusercontent.com/assets/328122/4543047/d1569f28-4e27-11e4-800e-2996b4d72bf2.png)

With this change, the error message is dispalyed inside the `pre` HTML tag to properly render the new lines.

![image](https://cloud.githubusercontent.com/assets/328122/4543084/11d14896-4e28-11e4-8e3e-31234a9d4898.png)