Learners on edX Platform can download python_lib.zip

The Open edX Platform is a learning management platform. Prior to commit 6740e75c0fdc7ba095baf88e9f5e4f3e15cfd8ba, edxapp has no built-in protection against downloading the python_lib.zip asset from courses, which is a concern since it often contains custom grading code or answers to course problems. This potentially affects any course using custom Python-graded problem blocks. The openedx/configuration repo has had a patch since 2016 in the form of an nginx rule, but this was only intended as a temporary mitigation. As the configuration repo has been deprecated and we have not been able to locate any similar protection in Tutor, it is likely that most deployments have no protection against python_lib.zip being downloaded. The recommended mitigation, implemented in commit 6740e75c0fdc7ba095baf88e9f5e4f3e15cfd8ba, restricts python_lib.zip downloads to just the course team and site staff/superusers.