Bug 1547730 - do py3 for cStringIO r=#build

Differential Revision: https://phabricator.services.mozilla.com/D28100

--HG--
extra : rebase_source : 419048b9789f19654bd6ceecc03f49e59fcf892d
extra : intermediate-source : ee3331ee87251ff67a9b55621d46efe655d58688
extra : source : ab5251d098f1f8bf9a6e258d26a6ab6b970421bf

python/mozbuild/mozpack/test/test_errors.py

@@ -11,13 +11,13 @@ from mozpack.errors import (
 )
 import unittest
 import mozunit
+import six
 import sys
-from cStringIO import StringIO
 
 
 class TestErrors(object):
     def setUp(self):
-        errors.out = StringIO()
+        errors.out = six.moves.cStringIO()
         errors.ignore_errors(False)
 
     def tearDown(self):

python/mozbuild/mozpack/test/test_mozjar.py

@@ -18,7 +18,7 @@ from collections import OrderedDict
 from mozpack.test.test_files import MockDest
 import unittest
 import mozunit
-from cStringIO import StringIO
+import six
 import mozpack.path as mozpath
 import os
 
@@ -291,7 +291,7 @@ class TestPreload(unittest.TestCase):
 
 class TestJarLog(unittest.TestCase):
     def test_jarlog(self):
-        s = StringIO('\n'.join([
+        s = six.moves.cStringIO('\n'.join([
             'bar/baz.jar first',
             'bar/baz.jar second',
             'bar/baz.jar third',