Some notes: In 3.x, cookielib is http.cookiejar. LWPCookieJar is a subclass of FileCookieJar. The module follows RFC 2109 and RFC 2965. RFC 6265 is labelled a 'PROPOSED STANDARD' that 'obsoletes' 2965, but its status is unclear to me. RFC 2965 says it has already been obsoleted. Of course, what matters in practice is what sites do. Cookielib was written to work with obsolete 2109 because that is what was mostly used at the time.

Paulie, please check what the older standards, that are the basis of cookielib, say about newlines in cookies. Also, please load the current 2.7 and 3.2 and test with 'non-compliant' sites.