The Environmental Variable TMSSSLACKONERROR will add a message to the Slack message in the event of an error in the executing process.
TMSSSLACKONERROR
set TMSSSLACKONERROR=true
$env:TMSSSLACKONERROR = "true"
export TMSSSLACKONERROR=true
TMSSSLACKURL TMSSSLACKUSER TMSSSLACKICON TMSSSLACKNOTES
Setting Environmental Variables