Code review fixes

core/url_data_cache.py

@@ -14,14 +14,13 @@ class URLDataCache(CachedSession):
     used across multiple threads, though note that URL lookups will block each other this way, so it is still better to
     create one of these objects per thread if possible."""
 
-    _lock = threading.Lock()
-
     def __init__(self, name):
         super().__init__(
             f"{CACHE_DIR}urls/{name}",
             expire_after=timedelta(days=1),
             allowable_codes=(200, 400, 401, 403, 404),
         )
+        self._lock = threading.Lock()
 
     def get(self, *args, **kwargs):
         with self._lock: