Bug 1606490 - /mozbuild/test/test_containers.py supports Python 3 r=firefox-build-system-reviewers,mshal

Differential Revision: https://phabricator.services.mozilla.com/D58462

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozbuild/test/python.ini

@@ -2,6 +2,7 @@
 subsuite = mozbuild
 
 [test_base.py]
+[test_containers.py]
 [test_expression.py]
 [test_jarmaker.py]
 [test_licenses.py]

python/mozbuild/mozbuild/test/python2.ini

@@ -37,6 +37,5 @@ skip-if = (os == "win")
 [frontend/test_reader.py]
 [frontend/test_sandbox.py]
 [test_artifact_cache.py]
-[test_containers.py]
 [test_dotproperties.py]
 [test_util.py]

python/mozbuild/mozbuild/test/test_containers.py

@@ -155,7 +155,7 @@ class TestOrderedDefaultDict(unittest.TestCase):
 
         self.assertEqual(test['foo'], 1)
 
-        self.assertEqual(test.keys(), ['foo', 'bar'])
+        self.assertEqual(list(test), ['foo', 'bar'])
 
     def test_defaults(self):
         test = OrderedDefaultDict(bool, {'foo': 1})
@@ -164,7 +164,7 @@ class TestOrderedDefaultDict(unittest.TestCase):
 
         self.assertEqual(test['qux'], False)
 
-        self.assertEqual(test.keys(), ['foo', 'qux'])
+        self.assertEqual(list(test), ['foo', 'qux'])
 
 
 class TestKeyedDefaultDict(unittest.TestCase):