presubmit_support: Fix tests on Python 3.

Bug: 1009814
Change-Id: I2c2a835fc4fa0a7fc9e68dfff680fb0beacb491e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1869535
Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
diff --git a/gerrit_util.py b/gerrit_util.py
index 0f5913c..a8a1c3b 100644
--- a/gerrit_util.py
+++ b/gerrit_util.py
@@ -12,8 +12,6 @@
 
 import base64
 import contextlib
-import cookielib
-import httplib  # Still used for its constants.
 import httplib2
 import json
 import logging
@@ -27,8 +25,6 @@
 import tempfile
 import time
 import urllib
-import urlparse
-from cStringIO import StringIO
 from multiprocessing.pool import ThreadPool
 
 import auth
@@ -37,6 +33,17 @@
 import metrics_utils
 import subprocess2
 
+if sys.version_info.major == 2:
+  import cookielib
+  import httplib
+  import urlparse
+  from cStringIO import StringIO
+else:
+  import http.cookiejar as cookielib
+  import http.client as httplib
+  import urllib.parse as urlparse
+  from io import StringIO
+
 LOGGER = logging.getLogger()
 # With a starting sleep time of 1.5 seconds, 2^n exponential backoff, and seven
 # total tries, the sleep time between the first and last tries will be 94.5 sec.