It looks like there are uninitialized variables in the Build instance.
You're constructing a Build instance yourself, but you should probably go through the API of the Jenkins instance to get the job and the build you're interested in.
import jenkinsapi
j = jenkinsapi.jenkins.Jenkins('http://jenkins:8080/')
job = j.get_job(JOB_NAME) # or j[JOB_NAME]
build = job.get_build(BUILD_ID)
print build.get_resultset()