open edx certivicate preview error

NameError at /certificates/user/6/course/course-v1:victim.com+VC101+2016_101

Undefined

Request Method: 	GET
Request URL: 	http://localhost:8000/certificates/user/6/course/course-v1:victim.com+VC101+2016_101?preview=no-id-professional
Django Version: 	1.8.7
Exception Type: 	NameError
Exception Value:

Undefined

Exception Location: 	/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/mako/runtime.py in __str__, line 226
Python Executable: 	/edx/app/edxapp/venvs/edxapp/bin/python
Python Version: 	2.7.10