I just discovered that there's an error (that stops the whole process -> no exception catch) in convert submissions for annotation when a student is unenrolled from a course after having submitted an assignment.

Steps to reproduce:

• Create a course, add an assignment and enrol a user as a student
• As the student, submit an assignment (Word file)
• Unenrol the student from the course.
• Run the convert annotation task (make sure unoconv and ghostscript are configured correctly):

  php admin/tool/task/cli/schedule_task.php --execute=\\assignfeedback_editpdf\\task\\convert_submissions

• You will have the following error:

  Execute scheduled task: Prepare submissions for annotation (assignfeedback_editpdf\task\convert_submissions)

  Convert 1 submission attempt(s) for assignment 3

  ... used 7 dbqueries

  ... used 0.11418199539185 seconds

  Scheduled task failed: Prepare submissions for annotation (assignfeedback_editpdf\task\convert_submissions),error/nopermission

  Backtrace:

  * line 485 of /mod/assign/feedback/editpdf/classes/document_services.php: call to print_error()

  * line 98 of /mod/assign/feedback/editpdf/classes/task/convert_submissions.php: call to assignfeedback_editpdf\document_services::get_page_images_for_attempt()

  * line 137 of /admin/tool/task/cli/schedule_task.php: call to assignfeedback_editpdf\task\convert_submissions->execute()