I just did some googling, and I think you mean "set -e".  The command harness also puts some different colored highlighting on the commands it prints which makes it easier to see them when everything is installing.  If you really want to replace this script with the set command I guess we can.  I'd want to test it out again because some of the commands are executed inside the virtual machine and some are on the regular host.  Not sure if that will work as expected with set.  Don't have time to test now, will do it later.