Given that test_shlex.py tests for the current behavior, it is hard to call this a bug in the tracker sense of the term. I would only change with a new version. 

The manual just says "When operating in POSIX mode, shlex will try to be as close as possible to the POSIX shell parsing rules." but gives no reference to which authority it is following or what the rules are in either case. Manual section 23.2.2. Parsing Rules only discusses the differences between posix and non-posix rules, not the common rules.

I suspect this module was written well over a decade ago, maybe closer to two. Is it possible that earlier versions were different on this issue? Or is the 2008 version only cosmetically different some 1990s version?