run_isolated: support non-isolated commands

client/utils/tools.py

 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed by the Apache v2.0 license that can be
 # found in the LICENSE file.
 
 """Various utility functions and classes not specific to any single area."""
 
 import atexit
+import contextlib
 import cStringIO
 import functools
 import json
 import logging
 import os
 import re
 import sys
 import threading
 import time
 
@@ skipping 291 matching lines @@
   a zip archive, we need to extract the file first.
   """
   global _ca_certs
   with _ca_certs_lock:
     if _ca_certs is not None and os.path.exists(_ca_certs):
       return _ca_certs
     # Some rogue process clears /tmp and causes cacert.pem to disappear. Extract
     # to current directory instead. We use our own bundled copy of cacert.pem.
     _ca_certs = zip_package.extract_resource(utils, 'cacert.pem', temp_dir='.')
     return _ca_certs
+
+
+@contextlib.contextmanager
+def noop_context():
+  """A noop context, can be used with `with` keyword."""
+  yield