Added enrollment question check to CourseModulePermissionBase

Before, the permission check would work by simply checking whether the module had opened yet. With this check, the module opening time is only checked if the exercise is not an enrollment question

Fixes #679

course/permissions.py

@@ -248,7 +248,8 @@ def has_object_permission(self, request: HttpRequest, view: Any, module: CourseM
         if module.status == CourseModule.STATUS.HIDDEN:
             return False
 
-        if not module.is_after_open():
+        #if this isn't an enrollment question and the module hasn't opened yet
+        if not (hasattr(view, 'exercise') and view.exercise.status in ('enrollment', 'enrollment_ext')) and not module.is_after_open():
             # FIXME: use format from django settings
             self.error_msg(
                 _('MODULE_PERMISSION_ERROR_NOT_OPEN_YET -- {date}'),