title: 500 server error when using jenkins python module build_job(job_name, parameters=) method
body: <p><code>server.build_job(self.job_full_name, parameters=params)</code> when parameters is not <code>None</code>, <code>jenkins.JenkinsException: Error in request. Possibly authentication failed [500]: Server Error</code> occurs. It works when <code>parameters=None</code>.</p>