config_service: use == for sentinel value

appengine/config_service/projects.py

 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Provides info about projects (service tenants)."""
 
 import logging
 
 from google.appengine.api import memcache
 from google.appengine.ext import ndb
@@ skipping 97 matching lines @@
     pid: ctx.memcache_get(pid, namespace=cache_ns)
     for pid in project_ids
   }
   yield cache_futs.values()
   result = {}
   missing = []
   for pid in project_ids:
     binary = cache_futs[pid].get_result()
     if binary is not None:
       # cache hit
-      if binary is PROJECT_DOES_NOT_EXIST_SENTINEL:
+      if binary == PROJECT_DOES_NOT_EXIST_SENTINEL:
         result[pid] = None
       else:
         cfg = project_config_pb2.ProjectCfg()
         cfg.ParseFromString(binary)
         result[pid] = cfg
     else:
       # cache miss
       missing.append(pid)
 
   if missing:
@@ skipping 59 matching lines @@
   # TODO(nodir): optimize
   assert isinstance(project_ids, list)
   if not project_ids:
     return project_ids
   assert all(pid for pid in project_ids)
   all_project_ids = set(p.id for p in get_projects())
   return [
     pid for pid in project_ids
     if pid in all_project_ids
   ]