some trace in stderr
This is stderr
lib/utility.bash: line 9: return 7
ERROR 7: [return 7]
	            lib/utility.bash:9	suite
	            lib/utility.bash:3	blabla
	                  useless.sh:8	F2
	                 useless.sh:19	F1
	                 useless.sh:23	main
	                 useless.sh:35	<main>