fix(severity): Initialize unbounded variable (#68219)

fixes SENTRY-34RZ

Author: snigdhas

src/sentry/event_manager.py

@@ -1836,6 +1836,7 @@ def _create_group(project: Project, event: Event, **group_creation_kwargs: Any)
     group_data.setdefault("metadata", {}).update(sdk_metadata_from_event(event))
 
     # add severity to metadata for alert filtering
+    severity: Mapping[str, Any] = {}
     try:
         group_type = group_creation_kwargs.get("type", None)
         severity = _get_severity_metadata_for_group(event, project.id, group_type)

tests/sentry/event_manager/test_priority.py

@@ -134,3 +134,15 @@ def test_killswitch_on(self, mock_get_severity_score: MagicMock):
         assert event.group.priority == PriorityLevel.HIGH
         assert event.group.get_event_metadata()["initial_priority"] == PriorityLevel.HIGH
         assert mock_get_severity_score.call_count == 1
+
+    @patch("sentry.event_manager._get_severity_metadata_for_group", return_value={})
+    def test_severity_error(self, mock_get_severity_metadata_for_group):
+        event = EventManager(
+            make_event(level=logging.WARNING, fingerprint=["def"], platform="python")
+        ).save(self.project.id)
+
+        assert event.group
+        assert "severity" not in event.group.get_event_metadata()
+        assert event.group.priority == PriorityLevel.MEDIUM
+        assert event.group.get_event_metadata()["initial_priority"] == PriorityLevel.MEDIUM
+        assert mock_get_severity_metadata_for_group.call_count == 1