add notice on asciidoc source code formatting

Author: Xronophobe

chapter_09_docker.asciidoc

@@ -388,6 +388,10 @@ TIP: I'm deliberately choosing a different port to run Dockerised Django on (888
 
 I'll use the `--failfast` option to exit as soon as a single test fails:
 
+// CSANAD:  are line breaks necessary below and at other occurrences of
+//          --failfast? it does keep the asciidoc lines of source below 80
+// characters but there are some wider lines elsewhere.
+
 [role="small-code"]
 [subs="specialcharacters,macros"]
 ----