Fix tests for nbgrader submit
Fix tests for nbgrader submit

ellisonbg/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,jhamrick/nbgrader,modulexcite/nbgrader,modulexcite/nbgrader,EdwardJKim/nbgrader,jhamrick/nbgrader,jhamrick/nbgrader,jdfreder/nbgrader,ellisonbg/nbgrader,dementrock/nbgrader,jupyter/nbgrader,alope107/nbgrader,EdwardJKim/nbgrader,MatKallada/nbgrader,dementrock/nbgrader,ellisonbg/nbgrader,jupyter/nbgrader,jdfreder/nbgrader,MatKallada/nbgrader,ellisonbg/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,alope107/nbgrader,jhamrick/nbgrader,jupyter/nbgrader