Improve error reporting consistency and ensure SEMI_STATIC_URL_DATA_CACHE caches 400-series responses from the server so we don't keep requesting summit/park/bunker data for a reference that the user typod and doesn't actually exist.

core/cache_utils.py

@@ -8,8 +8,11 @@ from requests_cache import CachedSession
 # of time has passed. This is used throughout Spothole to cache data that does not change
 # rapidly. The ThreadSafeSession construct here protects it against some multithreading
 # contention weirdness we sometimes used to see on startup where the cache was hammered
-# pretty hard.
-_session = CachedSession("cache/semi_static_url_data_cache", expire_after=timedelta(days=30))
+# pretty hard. The expanded list of allowable_codes ensures we also cache and return 400-type
+# responses, e.g "this SOTA summit ref doesn't actually exist", to avoid hammering remote
+# servers for data they've told us they can't provide.
+_session = CachedSession("cache/semi_static_url_data_cache", expire_after=timedelta(days=30),
+                         allowable_codes=(200, 400, 401, 403, 404))
 _lock = threading.Lock()