I was uncertain from Ethan's post what does work best. "endless errors with both 'spawn", "Only 'fork' works...but without graphics", "method='spawn'and ... does work".  Do the 1st and 3rd sentences mean that spawn + graphics fails without the proper additional code but does work with it?  Should the 2nd sentence be "fork only works without graphics" rather than starting with 'only fork'?

If so, this would suggest that the default should depend on whether there is a graphic import ;-).  In any case, how to use successfully use multiprocessing with graphics on Mac should be documented.