Collect errors

[johnmhoran]

[@MaJuRG comment] stop printing error messages to the console, and log the errors instead in the output.

[johnmhoran]

[@MaJuRG comment] A simple place to start might be defining message strings for the various custom exceptions we have.

see: https://github.com/nexB/conan/blob/develop/src/conan/image_v10.py at line 190-192

[steven-esser]

Another simple way to start is to just add an 'error' field to our DeltaCode object.

That way, when exceptions get raised etc, we just collect them in this errors field.

When we go to output, all we need is a quick check and then dump the error messages out.

[johnmhoran]

@MaJuRG Do we still want to add an error attribute to the DeltaCode class and collect all exceptions there?

[steven-esser]

The initial additions for this ticket have been merged. Will track new progress on new tickets.