Add "fail" function to utils

The function prints an error message to stderr and exits or returns with
a code of 1 based on the fail mode, which is passed as an input. If the
file is being sourced, then "return" would be passed in; else "exit"
would be passed in. This function invokes the say function created
earlier with the error formatting mode.

scripts/utils.sh

@@ -43,4 +43,12 @@ say () {
     *) # Unknown error
       ;;
   esac
+}
+
+# Prints an error message to stderr and exits (or returns) with a code of 1
+fail () {
+  local mode=${1}
+  local msg=( "${@:2}" )
+  say error "${msg[@]}"
+  $mode 1
 }