Use import from six.moves to import the queue module

The name of the synchronized queue class is queue instead of
Queue in Python3.

Change-Id: I89ea14e8d17cd37706752700cedb66b28d347fa2
diff --git a/tests/base.py b/tests/base.py
index 01b42f2..61ee912 100755
--- a/tests/base.py
+++ b/tests/base.py
@@ -21,7 +21,7 @@
 import logging
 import os
 import pprint
-import Queue
+from six.moves import queue as Queue
 import random
 import re
 import select
diff --git a/zuul/lib/gerrit.py b/zuul/lib/gerrit.py
index f72dd97..30fb6fe 100644
--- a/zuul/lib/gerrit.py
+++ b/zuul/lib/gerrit.py
@@ -17,7 +17,7 @@
 import select
 import json
 import time
-import Queue
+from six.moves import queue as Queue
 import paramiko
 import logging
 import pprint
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index 922d815..09fda72 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -20,7 +20,7 @@
 import logging
 import os
 import pickle
-import Queue
+from six.moves import queue as Queue
 import re
 import sys
 import threading