Fix error caused by access of un-enrolled user trying to attempt a assessment.
Merge branch 'development' of https://github.com/Coursemology/coursemology.org into undefined_method_levels
Add back permission check.
Merge branch 'development' of https://github.com/Coursemology/coursemology.org into undefined_method_levels
Simpler enrollment checking.
Merge pull request #181 from DIdiHL/undefined_method_levels

Undefined method levels