SVN having credential problems with Jenkins running as SYSTEM
Create a new Jenkins job, and use Subversion as the revision control system. Put in the URL of the Subversion repository you want to manipulate in your Python script. Under the URL will appear a link to let you set the login. Click the link and log in.
Once you're done, you can delete the job. The whole purpose was to allow Jenkins to set up Subversion to allow that user to login in for that repository URL.