As long as the weather is warm enough, the snake is properly settled in as was said above, and the snake has had about 2 days to digest it's last meal without disturbances, then there's no problem handling it, inside or out.

Personally I can handle my snakes while they're in shed, none of them get particularly crabby or stressed, but that's a matter of knowing your snake. If your snake seems to be high-strung, then I would refrain from handling during the shed cycle because it could stress them out enough to give them a bad shed.