* Changed an Assert error message in the `FileReadingMessageSource` to make the requirements when using an external scanner clearer, and added some explanatory comments. * Removed use of 'local' to eliminate confusion. * Added javadoc addendum
* Changed an Assert error message in the `FileReadingMessageSource` to make the requirements when using an external scanner clearer, and added some explanatory comments. * Removed use of 'local' to eliminate confusion. * Added javadoc addendum