Fix getting label by name (#5414)

# What this PR does
Handle JSONDecodeError on getting label key by name

## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

engine/apps/labels/models.py

@@ -1,5 +1,6 @@
 import logging
 import typing
+from json import JSONDecodeError
 
 from django.db import models
 from django.utils import timezone
@@ -44,7 +45,7 @@ def get_or_create_by_name(cls, organization: "Organization", key_name: str) -> t
             label, _ = LabelsAPIClient(organization.grafana_url, organization.api_token).get_label_by_key_name(
                 label_key
             )
-        except LabelsRepoAPIException as e:
+        except (LabelsRepoAPIException, JSONDecodeError) as e:
             logger.error(f"Failed to get or create label key {key_name} for organization {organization.id}: {e}")
             return None
 

engine/apps/labels/tests/test_labels_cache.py

@@ -1,3 +1,4 @@
+from json import JSONDecodeError
 from unittest.mock import call, patch
 
 import pytest
@@ -165,6 +166,12 @@ def test_get_or_create_label_key_cache_by_name(make_organization):
     organization = make_organization()
     label_key_data = {"id": "testid", "name": "testname", "prescribed": False}
 
+    # test empty response from label repo (json decode error)
+    with patch.object(LabelsAPIClient, "get_label_by_key_name", side_effect=JSONDecodeError("test", "test", 0)):
+        label = LabelKeyCache.get_or_create_by_name(organization, label_key_data["name"])
+
+    assert label is None
+
     # test label does not exist in labels repo
     with patch.object(LabelsAPIClient, "get_label_by_key_name", side_effect=LabelsRepoAPIException("test", "test")):
         label = LabelKeyCache.get_or_create_by_name(organization, label_key_data["name"])