Abort

makes it possible to abort entire action from subcard

also includes other improvements to exception handling and some touch-ups
I can see adding that, Gerry.  One thing to note is that a failure on any subcard will already cause a failure of the whole save (it's basically like a field validation in a form).  The success of a subcard is more ambiguous.

Philipp, good ideas.  It would be nice if there were a little more obvious parallelism among the three/four variants...