fix: learning_sequences missing courses now return 404 (not 500)

We weren't properly catching the CourseOutlineData.DoesNotExist error
before this commit. TNL-7979

openedx/core/djangoapps/content/learning_sequences/tests/test_views.py

@@ -70,6 +70,15 @@ class CourseOutlineViewTest(CacheIsolationTestCase, APITestCase):  # lint-amnest
         result = self.client.get(self.course_url)
         assert result.status_code == 403
 
+    def test_non_existent_course_404(self):
+        """
+        We should 404, not 500, when asking for a course that isn't there.
+        """
+        self.client.login(username='staff', password='staff_pass')
+        fake_course_key = self.course_key.replace(run="not_real")
+        result = self.client.get(self.url_for(fake_course_key))
+        assert result.status_code == 404
+
     def test_deprecated_course_key(self):
         """
         For now, make sure you need staff access bits to use the API.

openedx/core/djangoapps/content/learning_sequences/views.py

@@ -12,13 +12,15 @@ from edx_rest_framework_extensions.auth.jwt.authentication import JwtAuthenticat
 from edx_rest_framework_extensions.auth.session.authentication import SessionAuthenticationAllowInactiveUser
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.keys import CourseKey
-from rest_framework.views import APIView
-from rest_framework.response import Response
 from rest_framework import serializers
+from rest_framework.exceptions import NotFound
+from rest_framework.response import Response
+from rest_framework.views import APIView
 import attr  # lint-amnesty, pylint: disable=unused-import
 
 from openedx.core.lib.api.permissions import IsStaff
 from .api import get_user_course_outline_details
+from .data import CourseOutlineData
 
 User = get_user_model()
 log = logging.getLogger(__name__)
@@ -165,7 +167,11 @@ class CourseOutlineView(APIView):
         user = self._determine_user(request)
 
         # Grab the user's outline and send our response...
-        user_course_outline_details = get_user_course_outline_details(course_key, user, at_time)
+        try:
+            user_course_outline_details = get_user_course_outline_details(course_key, user, at_time)
+        except CourseOutlineData.DoesNotExist:
+            raise NotFound()
+
         serializer = self.UserCourseOutlineDataSerializer(user_course_outline_details)
         return Response(serializer.data)