Add storage validation to the status endpoint

Fixes #1659

health/services.py

@@ -1,6 +1,6 @@
 import logging
 from data.model import health
-from app import build_logs
+from app import build_logs, storage
 
 
 logger = logging.getLogger(__name__)
@@ -32,11 +32,20 @@ def _check_redis(app):
   """ Returns the status of Redis, as accessed from this instance. """
   return build_logs.check_health()
 
+def _check_storage(app):
+  """ Returns the status of storage, as accessed from this instance. """
+  try:
+    storage.validate(storage.preferred_locations, app.config['HTTPCLIENT'])
+    return True
+  except:
+    return False
+
 
 _SERVICES = {
   'registry_gunicorn': _check_registry_gunicorn,
   'database': _check_database,
-  'redis': _check_redis
+  'redis': _check_redis,
+  'storage': _check_storage,
 }
 
 def check_all_services(app, skip):