honestly, in my exp with an constrictor, the bites usually aren't bad.....9 times out of 10, they strike, but dont grab/coil....almost as if they realize "whooops...thats not food"

but...in the case that a snake constricts, it can be a problem
a while back i was helping a local shop owner handle an 8ft albino burmese, and somewhere between getting it out of its tank, and taking it to its feeding area, it decided to give me a nice "hug" - but....it relinquished eventually....but left some bruising, and hurt pretty bad....i'm assuming if it would have bitten, it would have been alot worse