Ah yes, good point - just another idea while I think of it, and @eteq and @iguananaut can comment (so @jdnc, don't change anything for now) - what about simply raising the exception as soon as ``initialize_options`` is called, then there's no need to replicate all the user options since the exception will be raised before the options are initialized. Or is ``initialize_options`` not guaranteed to be called before ``run``?