Allow run_remote_tests to proceed with inaccessible sheriffs

A modification in CL169724 made the run_remote_tests script
retrieve sheriffs for the google build tree for reporting
failures.  Outside of google, behind a typical proxied
corporate firewall, the defauilt URL specified in the
global_config.ini file fails the urlopen().read() call with
a httplib.BadStatusLine exception.  This was NOT caught by
the default handler that logs a message and allows the
caller to proceed without that sheriff.  This regression
caused the entire run_remote_tests script to fail.

This patch adds an additional exception handler to catch a
wider range of exceptions, log an message, and proceed
without that sheriff.

BUG=none
TEST=run_remote_tests from behind proxied firewall

Change-Id: Ife65b244291acd91117553f0a68ef661f267040d
Reviewed-on: https://chromium-review.googlesource.com/171481
Tested-by: Paul Drews <paul.drews@intel.com>
Reviewed-by: Alex Miller <milleral@chromium.org>
Commit-Queue: Paul Drews <paul.drews@intel.com>
diff --git a/server/site_utils.py b/server/site_utils.py
index f3acdb7..ab8f496 100644
--- a/server/site_utils.py
+++ b/server/site_utils.py
@@ -5,6 +5,8 @@
 
 import logging
 import re
+import urllib2
+import httplib
 
 from autotest_lib.client.common_lib import base_utils, global_config
 from autotest_lib.server.cros.dynamic_suite import constants
@@ -89,6 +91,9 @@
         except (ValueError, IOError) as e:
             logging.warning('could not parse sheriff from url %s%s: %s',
                              _CHROMIUM_BUILD_URL, sheriff_js, str(e))
+        except (urllib2.URLError, httplib.HTTPException) as e:
+            logging.warning('unexpected error reading from url "%s%s": %s',
+                             _CHROMIUM_BUILD_URL, sheriff_js, str(e))
         else:
             ldaps = re.search(r"document.write\('(.*)'\)", url_content)
             if not ldaps: