Submitted by Don Colton at BYU Hawaii:

While giving the 030 Workbook 3 Lab Test, I had a student who created
directories instead of files.  This caused your grading script to
crash.

Example Task:  Create file x, add "y" to it.

Correct response:  echo "y" > x

Student's incorrect response:

    mkdir x
    cp "y" x

Your grading script dies on this.  It tells the student to report the
problem to the instructor.

This happened with another student on a workbook lesson, so it is not
just limited to that particular lab test.