Change mode code import so it's more verbose
Change mode code import so it's more verbose

Now it will raise an exception if there’s a problem importing custom
mode code instead of silently swallowing it and deferring to the
built-in mode code

spierepf/mpf,missionpinball/mpf,spierepf/mpf,qcapen/mpf,missionpinball/mpf,qcapen/mpf