One remark to previous message:
the first time i created shlex object in non-POSIX mode (the default), 
in later it's in POSIX mode (due to the third parameter to shlex being 
True). The bug in question manifests only in POSIX mode.

BTW, that so-called POSIX mode would be more POSIX-ish, if instead of 
comparing characters with a fixed, short list, would use the ctype() 
function as found in standard C library. The functions takes current 
locale (setable in process) into account when deciding what is leter, 
whitespace, punctuation etc.