@carsten.klein: there is no such thing as an “original RFC”. The RFCs that have been produced on the subject of cookies, 2109 and 2965, were drawn up long after user-agents implemented cookies. Their attempts to clean up the warts of cookies and implement new features have completely failed. Their strictures are not obeyed by user agents; they are irrelevant and should not be used as the basis for any server-side cookie implementation.

The nearest to an original standard for cookies is the Netscape cookie-spec (see eg http://curl.haxx.se/rfc/cookie_spec.html), which is far too woolly to really count as a real specification, but which allows all but `;`, `,` and space, and in practice browsers do typically allow all characters that do not already serve as delimiters. Python should be liberal in what it accepts.