Improve error reporting for eval examples

[chrisvanrun]

See this commit: DIAGNijmegen/rse-workshop-2024@94def3b

No traceback is generally shown at the current style: only the error.

[chrisvanrun]

Only this is shown without any changes, completely unclear which line this happened.

[chrisvanrun]

Adding a managed que instead of a managed list of the error and cancel all the workers, then raise the error seems like the cleanest approach here. Unlike the hacky printing in the linked commit.