lint: fix wrong-import-order warnings

Newer pylint is able to enforce PEP8 module ordering.  Respect it.

BUG=chromium:863669
TEST=`cros lint` no longer reports this

Change-Id: I4d4f7669d6dcced7e0d1ceeffd949a818b867055
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1768870
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/upload_symbols_unittest.py b/scripts/upload_symbols_unittest.py
index 77dde83..c4b2968 100644
--- a/scripts/upload_symbols_unittest.py
+++ b/scripts/upload_symbols_unittest.py
@@ -10,7 +10,6 @@
 import BaseHTTPServer
 import errno
 import itertools
-import mock
 import os
 import signal
 import socket
@@ -19,6 +18,8 @@
 import time
 import urllib2
 
+import mock
+
 # We specifically set up a local server to connect to, so make sure we
 # delete any proxy settings that might screw that up.  We also need to
 # do it here because modules that are imported below will implicitly