tests/datawizard/write_only_tmp_buffer.c: fix message

tests/datawizard/write_only_tmp_buffer.c

@@ -72,7 +72,7 @@ static void display_var(void *descr[], __attribute__ ((unused)) void *_args)
 	char *buf = (char *)STARPU_VECTOR_GET_PTR(descr[0]);
 	if (*buf != 42)
 	{
-		FPRINTF(stderr, "Value = '%c' (should be '%c')\n", *buf, 42);
+		FPRINTF(stderr, "Value = <%c> (should be <%c>)\n", *buf, 42);
 		exit(-1);
 	}
 }