check_course didn't have the right exception being caught.

lms/djangoapps/courseware/courses.py

@@ -8,6 +8,7 @@ from django.http import Http404
 
 from xmodule.course_module import CourseDescriptor
 from xmodule.modulestore.django import modulestore
+from xmodule.modulestore.exceptions import ItemNotFoundError
 
 log = logging.getLogger(__name__)
 
@@ -29,7 +30,7 @@ def check_course(course_id, course_must_be_open=True, course_required=True):
         try:
             course_loc = CourseDescriptor.id_to_location(course_id)
             course = modulestore().get_item(course_loc)
-        except KeyError:
+        except (KeyError, ItemNotFoundError):
             raise Http404("Course not found.")
         
         if course_must_be_open and not course.has_started():