IMP: tests readability and runtime error handling

Change describe display to add underline in order to make it more
noticeable in a stream of logs
Add a `fatal` message when catching a runtime error (until
`$totalerrors` has not been modified yet)

tests/lib.sh

@@ -8,7 +8,7 @@
 # describe <STRING>
 describe() {
     # shellcheck disable=2154
-    printf "\033[36mxxx %s::%s \033[0m\n" "$name" "$*"
+    printf "\033[4;36mxxx %s::%s \033[0m\n" "$name" "$*"
 }
 
 # Register an assertion on an audit before running it