tools/lib/atusb-common.c (atusb_open): give more detailed error message on EPERM
tools/lib/atusb-common.c (atusb_open): give more detailed error message on EPERM

cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan