I tested setting cookies with ":" in the cookie name in both firefox and google-chrome. They both seem to allow and store the cookie with ":" in them.
Firefox sent a request header like this:

Set-Cookie	test:value=solution:is:he

the cookie with name containing ; or , failed.

The patched attached tries to silence the error with SimpleCookie. I am not sure how far it is going to help. I believe, we could just allow it from 3.3 onwards or create a new BrowserCookie class which is more lenient than SimpleCookie.

As far I see, the allowing ":" in the Legalchars seem to have met with negative votes because it was not in RFC, but well it seems some kind of de-facto acceptable behaviour with browsers, so having from a new version may not cause any harm. +1 to that. I can modify the tests from the attached patch.