Warning messages in reports

[adelavega]

Currently, report failures just show an ugly traceback.

It would be nicer and more informative if we were to catch certain types of errors (that are common) and gracefully fail, and offer suggestions.

For example: if n/as are found after transformations are applied (and thus would crash on fitlins), give a warning and suggest dropping n/as or scale + replace n/a.

[adelavega]

Part of this is accomplished by wrapping the error code with a custom message with a try, catch exception.

Renaming this to focus on sending warning messages (with a new field) that can be seen by the user.