Steps to reproduce:
Download Kylo HDP Sandbox and start image. No issues with any menu here
Check out the latest code from git and build RPM.
Install RPM is sandbox
Bring up all apps
Login and go to Categories menu. Error occurs. See the attached stacktrace.txt
Did a fresh 0.9.0 install.
Created feeds, categories.
Upgraded to 0.9.1 with rpm from master.
Upgrade went fine.
When Kylo comes up, categories show up ok.
Can't reproduce. Closing the issue.