It appears like Python's library Suds recently added the following to sxbasic.py :
Import.bind('http://schemas.xmlsoap.org/soap/encoding/')
For some reason, this addition to the XML payload (in the form SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/") consistently returns an error from my Siebel webservice. After spending 2 days tracking down the issue (I'm a bit of a newb with SOAP) I downloaded the suds source, commented out this line in sxbasic.py and rebuild the library. And the line from rpc.py that reads env.set('%s:encodingStyle' % envns[0], 'http://schemas.xmlsoap.org/soap/encoding/'). Now everything works.
Not sure why this is. If anyone can shed light I would appreciate it. More importantly, if anyone can tell me how to override this without having to build my own version of the library, I would be most grateful.
Thanks! Jay