Add build slave side support for the new swarming.py script.

scripts/slave/swarming/swarming_utils.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Code to find swarming_client."""
 
 import os
+import sys
+
+from common import find_depot_tools  # pylint: disable=W0611
+
+# From depot_tools/
+import subprocess2
 
 
 def find_client(base_dir):
   """Returns the path to swarming_client if found.
 
   |base_dir| will be in general os.getcwd(), so the script is very dependent on
   CWD. CWD should be the base directory of the checkout. It has always been the
   case.
   """
   src_swarming_client = os.path.join(
       base_dir, 'src', 'tools', 'swarming_client')
   if os.path.isdir(src_swarming_client):
     return src_swarming_client
 
   # This is the previous path. This can be removed around 2013-12-01.
   src_swarm_client = os.path.join(base_dir, 'src', 'tools', 'swarm_client')
   if os.path.isdir(src_swarm_client):
     return src_swarm_client
+
+
+def get_version(client):
+  """Returns the version of swarming.py client tool, if available."""
+  try:
+    version = subprocess2.check_output(
+        [
+          sys.executable,
+          os.path.join(client, 'swarming.py'),
+          '--version',
+        ])
+  except (subprocess2.CalledProcessError, OSError):
+    return None
+  return map(int, version.split('.'))

[Isaac (away), 2013/08/27 01:35:20]

This returns a generator -- convert to a list?

[M-A Ruel, 2013/08/27 12:23:37]

http://docs.python.org/2/library/functions.html#map
"The iterable arguments may be a sequence or any iterable object; the result is
always a list."

Note that I could have used:
return [int(i) for i in version.split('.')]
but it's longer to type. :) I don't really mind either way.

[Isaac (use chromium), 2013/08/27 17:43:00]

Hmm, I must be remembering correctly.  Weird.

I use map for situations like this too.