It tries to mimic the handling of the mod.exploit_simple later, where call stacks are print then there is an exception different than OptionValidateError. I guess because there is module code executed. Since get_auto_target will try to run module code too, I've just tried to mimic the handling, so there isn't an unexpected behaviour. 

But on the other hand, that's true which it is giving the module the opportunity to go further, so maybe a call stack here is too much. We can discuss it later on the time, once you're back from vacation ;) thanks a lot for start to look into it!