This is related to [ 432621 ] httplib: multiple Set-Cookie headers, which I was unable to re-open.

The workaround that was adopted in the previous bug tracker item was to combine multiple set-cookie headers received from the server, into a single set-cookie element in the headers dictionary, with the cookies joined into a comma-separated string.

The problem arises when a comma character appears inside the 'expires' field of one of the cookies.  This makes it difficult to split the cookie headers back apart.  The comma character should be escaped, or a different separator character used.

i.e.

expires=Sun, 17-Jan-2038 19:14:07 GMT

For now I am using the workaround that gstein suggested, use response.msg.getallmatchingheaders()

Python 2.3 has this behavior, and probably later versions.