Using Python with suds in JIRA 4.0 works for fetching issues but updating fails with a SAXException. Example:
from suds.client import Client as X; X('wsdl').upd('sess','BUG1',[{'fld':'nm'}])
I experienced a similar issue when trying to update issues using suds on a legacy JIRA installation. The SAXException was triggered due to a mismatch in expected XML formatting. I ultimately found that adding custom type mappings and ensuring that all namespaces were correctly set up in the SOAP envelope helped in resolving this error. Adjusting the suds client settings to disable certain strict parsing options also provided some relief. It might be worth exploring these modifications in your code so that the XML sent during the update conforms with what JIRA expects.
In my experience, the SAXException issue when working with JIRA using suds often stemmed from subtle differences in how the SOAP messages were structured between creating and updating issues. I found that tweaking the XML payload manually before sending it could resolve the error, particularly by ensuring the correct encoding and namespace definitions. Additionally, switching to a more recent version of suds or using an alternative SOAP client sometimes mitigated such issues. Analyzing the raw SOAP request helped identify discrepancies and adjust the configuration accordingly.