Add exception_name helper to hmmmgrader.py
Add exception_name helper to hmmmgrader.py

This resolves an error.

CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader