Be nice and report them errors

mortal-webpack is designed not to throw any exceptions at run-time, and the way it communicates errors is in return values of function calls. When you generate configuration, the process may fail and then you're expected to report those failures to the user through some means.

Out of the box, mortal-webpack ships an error reporter that formats messages nicely, writes them to STDERR (or anywhere), and optionally exit the process with a proper exit code to make it integrate with shell tools.