By default, bash will ignore any failing commands and happily proceed to execute the next ones. This is usually not the behavior the we want in provisioning script (or ever in scripts, actually): if one step of the provisioning fails, it doesn't make much sense to proceed with the following ones.
This simple patch uses set -e to ask bash to abort the whole script if
any command within it fails, leading to outputs that are easier to parse
since the commands following a failing one will usually fail also,
hiding the root cause.