This change makes the cron jobs check for the existence of a Python virtual environment, set up in a
venv directory. If there is no virtual environment, the cron job will fail with an error and a message to stdout (which should end up in someone's root@ server mailbox somewhere). This environment should be set up when the Debian package is updated to a new version (in postinst).
Note: before this package is installed, the mahara manual directory should be checked out to the latest
16.10_STABLE branch which should contain the
requirements.txt file, which is required for the postinst to correctly install the virtual environment.