run_isolated: support non-isolated commands

client/utils/tools.py

Index: client/utils/tools.py
diff --git a/client/utils/tools.py b/client/utils/tools.py
index 506143d7e3310b2ba5f6d275da251ed9182db8e7..9889797079f2efb49f97f3a9c6492fa4eca9a874 100644
--- a/client/utils/tools.py
+++ b/client/utils/tools.py
@@ -5,6 +5,7 @@
 """Various utility functions and classes not specific to any single area."""
 
 import atexit
+import contextlib
 import cStringIO
 import functools
 import json
@@ -316,3 +317,9 @@ def get_cacerts_bundle():
     # 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