SimpleHTTPRequestHandler is not part of httplib.  Did you mean to refer to module SimpleHTTPServer rather than httplib, perhaps?

I don't see the particular bit of code you refer to (neither in httplib nor in module SimpleHTTPServer), but re the general issue:

Regardless of the fact that RFC 2616 ss. 4.2 says headers MUST be able to be combined with commas, Netscape Set-Cookie headers simply don't work that way, and Netscape Set-Cookie headers are here to stay.  So, Set-Cookie headers must not be combined.

(Quoting does not help, because Netscape Set-Cookie headers contain cookie values that 1. may contain commas and 2. do not support quoting -- any quote (") characters are in fact part of the cookie value itself rather than being part of a quoting mechanism.  And there is no precedent for any choice of delimter other than a comma, nor for any other Netscape Set-Cookie cookie value quoting mechanism.)