file_utils.py: fix urllib2 attribute error.

urrllib2.URLError's message atrribute is obj.message not obj.msg.

BUG=chrome-os-partner:52264,chrome-os-partner:54277
TEST=none

Change-Id: Ifc46a64cdfb05871eaee38ff5c854e0d3ac7d02f
Reviewed-on: https://chromium-review.googlesource.com/355683
Commit-Ready: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Ravi Chandra Sadineni <ravisadineni@chromium.org>
diff --git a/client/common_lib/file_utils.py b/client/common_lib/file_utils.py
index 17bdf2c..b17fdab 100644
--- a/client/common_lib/file_utils.py
+++ b/client/common_lib/file_utils.py
@@ -161,7 +161,7 @@
     except urllib2.URLError as e:
         e.msg = (("""URLError raised while retrieving file %s\n.
                         Reason = %s\n. Original Message = %s\n.""")
-                 % (remote_path, e.reason, e.msg))
+                 % (remote_path, e.reason, e.message))
         raise
 
     with open(local_path, 'wb') as local_file: