feat: add grades event bus event handler for rejected special exam

This commit adds an event bus event handler to the grades application. This event handler handles the EXAM_ATTEMPT_REJECTED Open edX event,
 which is emitted when a learner's exam attempt is rejected. The event handler creates a subsection grade override, overriding the grade to
 0.0.

lms/djangoapps/grades/signals/handlers.py

@@ -8,7 +8,7 @@
 
 from django.dispatch import receiver
 from opaque_keys.edx.keys import LearningContextKey
-from openedx_events.learning.signals import EXAM_ATTEMPT_VERIFIED
+from openedx_events.learning.signals import EXAM_ATTEMPT_REJECTED, EXAM_ATTEMPT_VERIFIED
 from submissions.models import score_reset, score_set
 from xblock.scorable import ScorableXBlockMixin, Score
 
@@ -322,3 +322,28 @@ def exam_attempt_verified_event_handler(sender, signal, **kwargs):  # pylint: di
 
     if should_override_grade_on_rejected_exam(course_key):
         undo_override_subsection_grade(user_data.id, course_key, usage_key, GradeOverrideFeatureEnum.proctoring)
+
+
+@receiver(EXAM_ATTEMPT_REJECTED)
+def exam_attempt_rejected_event_handler(sender, signal, **kwargs):  # pylint: disable=unused-argument
+    """
+    Consume `EXAM_ATTEMPT_REJECTED` events from the event bus. This will trigger a subsection override.
+    """
+    from ..api import override_subsection_grade
+
+    event_data = kwargs.get('exam_attempt')
+    override_grade_value = 0.0
+    user_data = event_data.student_user
+    course_key = event_data.course_key
+    usage_key = event_data.usage_key
+
+    override_subsection_grade(
+        user_data.id,
+        course_key,
+        usage_key,
+        earned_all=override_grade_value,
+        earned_graded=override_grade_value,
+        feature=GradeOverrideFeatureEnum.proctoring,
+        overrider=None,
+        comment=None,
+    )

lms/djangoapps/grades/tests/test_handlers.py

@@ -10,10 +10,13 @@
 from opaque_keys.edx.keys import CourseKey, UsageKey
 from openedx_events.data import EventsMetadata
 from openedx_events.learning.data import ExamAttemptData, UserData, UserPersonalData
-from openedx_events.learning.signals import EXAM_ATTEMPT_VERIFIED
+from openedx_events.learning.signals import EXAM_ATTEMPT_REJECTED, EXAM_ATTEMPT_VERIFIED
 
 from common.djangoapps.student.tests.factories import UserFactory
-from lms.djangoapps.grades.signals.handlers import exam_attempt_verified_event_handler
+from lms.djangoapps.grades.signals.handlers import (
+    exam_attempt_rejected_event_handler,
+    exam_attempt_verified_event_handler
+)
 from ..constants import GradeOverrideFeatureEnum
 
 
@@ -101,3 +104,30 @@ def test_exam_attempt_verified_event_handler(self, override_enabled, mock_undo_o
             )
         else:
             mock_undo_override.assert_not_called()
+
+    @mock.patch('lms.djangoapps.grades.api.override_subsection_grade')
+    def test_exam_attempt_rejected_event_handler(self, mock_override):
+        exam_event_data = self._get_exam_event_data(self.student_user,
+                                                    self.course_key,
+                                                    self.usage_key,
+                                                    exam_type='proctored')
+        event_metadata = self._get_exam_event_metadata(EXAM_ATTEMPT_REJECTED)
+
+        event_kwargs = {
+            'exam_attempt': exam_event_data,
+            'metadata': event_metadata
+        }
+        exam_attempt_rejected_event_handler(None, EXAM_ATTEMPT_REJECTED, ** event_kwargs)
+
+        override_grade_value = 0.0
+
+        mock_override.assert_called_once_with(
+            self.student_user.id,
+            self.course_key,
+            self.usage_key,
+            earned_all=override_grade_value,
+            earned_graded=override_grade_value,
+            feature=GradeOverrideFeatureEnum.proctoring,
+            overrider=None,
+            comment=None,
+        )