Hotfix/lecture video logger exceptions

improved error handling, streamlined exceptions and logging statements to deal with the error that are occurring in prod:
File "/apps/icommons_lti_tools/lecture_video/views.py", line 146, in main
logger.exception('ObjectDoesNotExist, huid='+huid+', keyword='+keyword+', course_instance_id='+course_instance_id)

remove logger strings for hid, keyword and course_instance.
This works. You could still use the verbose statement above if it was transformed into `"huid=%s, keyword=%s...." % (var, var, ...)` -- `None` is handled by the formatter in that case.