Devserver: fix pylint errors in common_util.py.

BUG=chromium:344939
TEST=Unittests + pylint.

Change-Id: Ic798e58f258019aea563e30e39012db97a4728b4
Reviewed-on: https://chromium-review.googlesource.com/193992
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
diff --git a/devserver.py b/devserver.py
index 7caaadc..97cbded 100755
--- a/devserver.py
+++ b/devserver.py
@@ -990,7 +990,7 @@
                    'this setting enabled, this devserver instance serves as '
                    'just an Omaha server instance. In this mode, the '
                    'devserver enforces a few extra components of the Omaha '
-                   'protocol e.g. hardware class being sent etc.')
+                   'protocol, such as hardware class, being sent.')
   group.add_option('-u', '--urlbase',
                    metavar='URL',
                      help='base URL for update images, other than the '