v1.3 added the ability to catch the last exit code of the configured commands but if a command is missing and Powershell throws an exception, PS doesn't set $LastExitCode and the build succeeds. Rather than emit:

{{
<user's configured commands>
exit $LastExitCode
}}

It would be helpful to do:

{{
try

{ <user's configured commands> exit $LastExitCode } catch { write-host "Script threw an exception" write-host $error[0] exit 1 } }}

(or something). See MSDN and StackOverflow