Autotest: Change logging.warn() to logging.warning().

logging.warn() is deprecated. See
http://bugs.python.org/issue13235

Substitution was performed via
~/cros/src/third_party/autotest/files$ find ./ -type f | xargs sed -i 's/logging.warn(/logging.warning(/'

BUG=None.
TEST=There should be one-- and preferably only one --obvious way to do it.

Change-Id: Ie5665743121a49f7fbd5d1f47896a7c65e87e489
Reviewed-on: https://chromium-review.googlesource.com/198793
Commit-Queue: Ilja Friedel <ihf@chromium.org>
Tested-by: Ilja Friedel <ihf@chromium.org>
Reviewed-by: Alex Miller <milleral@chromium.org>
diff --git a/server/site_utils.py b/server/site_utils.py
index 7a6ad28..f34c923 100644
--- a/server/site_utils.py
+++ b/server/site_utils.py
@@ -233,7 +233,7 @@
     json_status = _get_lab_status(status_url)
     if json_status is None:
         # We go ahead and say the lab is open if we can't get the status.
-        logging.warn('Could not get a status from %s', status_url)
+        logging.warning('Could not get a status from %s', status_url)
         return
     _decode_lab_status(json_status, build)