I'd like to add that when supplying custom headers for things like UPNP (which uses SOAPACTION as a header to talk to frequently very limited servers), the library shouldn't mangle the headers in any way whatsoever and send them verbatim. 

(I consider that mangling to be a bug, and not a new feature. HTTP headers may be case-insensitve according to standards, but embedded implementations require us to have a degree of control over the headers, and failing to preserve header case is a bug.)

Right now I've had to replace httplib and urllib2 with my own custom code because the SOAPACTION header is capitalized and sent to the server as "Soapaction", which breaks the Intel embedded UPNP daemon.