specify metaclasses in a py3-compatible way

21 files changed, 106 insertions, 126 deletions

diff --git a/src/python/grpcio/tests/unit/_adapter/_proto_scenarios.py b/src/python/grpcio/tests/unit/_adapter/_proto_scenarios.py
index f55a7a23ea..c9f36636b5 100644
--- a/src/python/grpcio/tests/unit/_adapter/_proto_scenarios.py
+++ b/src/python/grpcio/tests/unit/_adapter/_proto_scenarios.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,12 +32,13 @@
 import abc
 import threading
 
+import six
+
 from tests.unit._junkdrawer import math_pb2
 
 
-class ProtoScenario(object):
+class ProtoScenario(six.with_metaclass(abc.ABCMeta)):
   """An RPC test scenario using protocol buffers."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def method(self):
diff --git a/src/python/grpcio/tests/unit/_links/_proto_scenarios.py b/src/python/grpcio/tests/unit/_links/_proto_scenarios.py
index f69ff51b16..acd4891390 100644
--- a/src/python/grpcio/tests/unit/_links/_proto_scenarios.py
+++ b/src/python/grpcio/tests/unit/_links/_proto_scenarios.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,13 +32,14 @@
 import abc
 import threading
 
+import six
+
 from tests.unit._junkdrawer import math_pb2
 from tests.unit.framework.common import test_constants
 
 
-class ProtoScenario(object):
+class ProtoScenario(six.with_metaclass(abc.ABCMeta)):
   """An RPC test scenario using protocol buffers."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def group_and_method(self):
diff --git a/src/python/grpcio/tests/unit/framework/common/test_control.py b/src/python/grpcio/tests/unit/framework/common/test_control.py
index 8d6eba5c2c..0387668b11 100644
--- a/src/python/grpcio/tests/unit/framework/common/test_control.py
+++ b/src/python/grpcio/tests/unit/framework/common/test_control.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,6 +33,8 @@ import abc
 import contextlib
 import threading
 
+import six
+
 
 class Defect(Exception):
   """Simulates a programming defect raised into in a system under test.
@@ -42,7 +44,7 @@ class Defect(Exception):
   """
 
 
-class Control(object):
+class Control(six.with_metaclass(abc.ABCMeta)):
   """An object that accepts program control from a system under test.
 
   Systems under test passed a Control should call its control() method
@@ -51,8 +53,6 @@ class Control(object):
   the system under test to simulate hanging, failing, or functioning.
   """
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def control(self):
     """Potentially does anything."""
diff --git a/src/python/grpcio/tests/unit/framework/common/test_coverage.py b/src/python/grpcio/tests/unit/framework/common/test_coverage.py
index a7ed3582c4..184621fb5c 100644
--- a/src/python/grpcio/tests/unit/framework/common/test_coverage.py
+++ b/src/python/grpcio/tests/unit/framework/common/test_coverage.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,13 +31,14 @@
 
 import abc
 
+import six
+
 # This code is designed for use with the unittest module.
 # pylint: disable=invalid-name
 
 
-class Coverage(object):
+class Coverage(six.with_metaclass(abc.ABCMeta)):
   """Specification of test coverage."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def testSuccessfulUnaryRequestUnaryResponse(self):
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/base_util.py b/src/python/grpcio/tests/unit/framework/face/testing/base_util.py
index 1df1529b27..60ab5bc0fe 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/base_util.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/base_util.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
 
 import abc
 
+import six
+
 # interfaces is referenced from specification in this module.
 from grpc.framework.base import util as _base_util
 from grpc.framework.base import implementations
@@ -43,7 +45,7 @@ _POOL_SIZE_LIMIT = 5
 _MAXIMUM_TIMEOUT = 90
 
 
-class LinkedPair(object):
+class LinkedPair(six.with_metaclass(abc.ABCMeta)):
   """A Front and Back that are linked to one another.
 
   Attributes:
@@ -51,8 +53,6 @@ class LinkedPair(object):
     back: An interfaces.Back.
   """
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def shut_down(self):
     """Shuts down this object and releases its resources."""
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
index 0613516421..2fc67f6292 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,6 +33,8 @@
 import abc
 import unittest  # pylint: disable=unused-import
 
+import six
+
 from grpc.framework.face import exceptions
 from tests.unit.framework.common import test_constants
 from tests.unit.framework.face.testing import control
@@ -43,12 +45,12 @@ from tests.unit.framework.face.testing import test_case
 
 
 class BlockingInvocationInlineServiceTestCase(
-    test_case.FaceTestCase, coverage.BlockingCoverage):
+    six.with_metaclass(abc.ABCMeta,
+    test_case.FaceTestCase, coverage.BlockingCoverage)):
   """A test of the Face layer of RPC Framework.
 
   Concrete subclasses must also extend unittest.TestCase.
   """
-  __metaclass__ = abc.ABCMeta
 
   def setUp(self):
     """See unittest.TestCase.setUp for full specification.
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/control.py b/src/python/grpcio/tests/unit/framework/face/testing/control.py
index 3960c4e649..0d40331e19 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/control.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/control.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,8 +33,10 @@ import abc
 import contextlib
 import threading
 
+import six
 
-class Control(object):
+
+class Control(six.with_metaclass(abc.ABCMeta)):
   """An object that accepts program control from a system under test.
 
   Systems under test passed a Control should call its control() method
@@ -43,8 +45,6 @@ class Control(object):
   the system under test to simulate hanging, failing, or functioning.
   """
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def control(self):
     """Potentially does anything."""
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/coverage.py b/src/python/grpcio/tests/unit/framework/face/testing/coverage.py
index f3aca113fe..9f5381069d 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/coverage.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/coverage.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,15 +31,15 @@
 
 import abc
 
+import six
+
 # These classes are only valid when inherited by unittest.TestCases.
 # pylint: disable=invalid-name
 
 
-class BlockingCoverage(object):
+class BlockingCoverage(six.with_metaclass(abc.ABCMeta)):
   """Specification of test coverage for blocking behaviors."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def testSuccessfulUnaryRequestUnaryResponse(self):
     raise NotImplementedError()
@@ -93,11 +93,9 @@ class BlockingCoverage(object):
     raise NotImplementedError()
 
 
-class FullCoverage(BlockingCoverage):
+class FullCoverage(six.with_metaclass(abc.ABCMeta, BlockingCoverage)):
   """Specification of test coverage for non-blocking behaviors."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def testParallelInvocations(self):
     raise NotImplementedError()
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
index 179f3a2f67..b707dcdf6c 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import abc
 import unittest
 
+import six
+
 from grpc.framework.face import interfaces
 from tests.unit.framework.common import test_constants
 from tests.unit.framework.face.testing import callback as testing_callback
@@ -43,12 +45,12 @@ from tests.unit.framework.face.testing import test_case
 
 
 class EventInvocationSynchronousEventServiceTestCase(
-    test_case.FaceTestCase, coverage.FullCoverage):
+    six.with_metaclass(abc.ABCMeta,
+    test_case.FaceTestCase, coverage.FullCoverage)):
   """A test of the Face layer of RPC Framework.
 
   Concrete subclasses must also extend unittest.TestCase.
   """
-  __metaclass__ = abc.ABCMeta
 
   def setUp(self):
     """See unittest.TestCase.setUp for full specification.
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
index 485524a356..4d27cbe186 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -34,6 +34,8 @@ import contextlib
 import threading
 import unittest
 
+import six
+
 from grpc.framework.face import exceptions
 from grpc.framework.foundation import future
 from grpc.framework.foundation import logging_pool
@@ -74,12 +76,12 @@ class _PauseableIterator(object):
 
 
 class FutureInvocationAsynchronousEventServiceTestCase(
-    test_case.FaceTestCase, coverage.FullCoverage):
+    six.with_metaclass(abc.ABCMeta,
+    test_case.FaceTestCase, coverage.FullCoverage)):
   """A test of the Face layer of RPC Framework.
 
   Concrete subclasses must also extend unittest.TestCase.
   """
-  __metaclass__ = abc.ABCMeta
 
   def setUp(self):
     """See unittest.TestCase.setUp for full specification.
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/interfaces.py b/src/python/grpcio/tests/unit/framework/face/testing/interfaces.py
index 5932dabf1e..87be836e2d 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/interfaces.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/interfaces.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,13 +31,14 @@
 
 import abc
 
+import six
+
 # cardinality is referenced from specification in this module.
 from grpc.framework.common import cardinality  # pylint: disable=unused-import
 
 
-class Method(object):
+class Method(six.with_metaclass(abc.ABCMeta)):
   """An RPC method to be used in tests of RPC implementations."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def name(self):
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/service.py b/src/python/grpcio/tests/unit/framework/face/testing/service.py
index ac0b89b6ee..dc0f204c04 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/service.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/service.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,16 +31,16 @@
 
 import abc
 
+import six
+
 # interfaces is referenced from specification in this module.
 from grpc.framework.face import interfaces as face_interfaces  # pylint: disable=unused-import
 from tests.unit.framework.face.testing import interfaces
 
 
-class UnaryUnaryTestMethodImplementation(interfaces.Method):
+class UnaryUnaryTestMethodImplementation(six.with_metaclass(abc.ABCMeta, interfaces.Method)):
   """A controllable implementation of a unary-unary RPC method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, request, response_callback, context, control):
     """Services an RPC that accepts one message and produces one message.
@@ -59,11 +59,9 @@ class UnaryUnaryTestMethodImplementation(interfaces.Method):
     raise NotImplementedError()
 
 
-class UnaryUnaryTestMessages(object):
+class UnaryUnaryTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for unary-request-unary-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def request(self):
     """Affords a request message.
@@ -93,11 +91,9 @@ class UnaryUnaryTestMessages(object):
     raise NotImplementedError()
 
 
-class UnaryStreamTestMethodImplementation(interfaces.Method):
+class UnaryStreamTestMethodImplementation(six.with_metaclass(abc.ABCMeta, interfaces.Method)):
   """A controllable implementation of a unary-stream RPC method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, request, response_consumer, context, control):
     """Services an RPC that takes one message and produces a stream of messages.
@@ -116,11 +112,9 @@ class UnaryStreamTestMethodImplementation(interfaces.Method):
     raise NotImplementedError()
 
 
-class UnaryStreamTestMessages(object):
+class UnaryStreamTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for unary-request-stream-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def request(self):
     """Affords a request message.
@@ -150,11 +144,9 @@ class UnaryStreamTestMessages(object):
     raise NotImplementedError()
 
 
-class StreamUnaryTestMethodImplementation(interfaces.Method):
+class StreamUnaryTestMethodImplementation(six.with_metaclass(abc.ABCMeta, interfaces.Method)):
   """A controllable implementation of a stream-unary RPC method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, response_callback, context, control):
     """Services an RPC that takes a stream of messages and produces one message.
@@ -180,11 +172,9 @@ class StreamUnaryTestMethodImplementation(interfaces.Method):
     raise NotImplementedError()
 
 
-class StreamUnaryTestMessages(object):
+class StreamUnaryTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for stream-request-unary-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def requests(self):
     """Affords a sequence of request messages.
@@ -214,11 +204,9 @@ class StreamUnaryTestMessages(object):
     raise NotImplementedError()
 
 
-class StreamStreamTestMethodImplementation(interfaces.Method):
+class StreamStreamTestMethodImplementation(six.with_metaclass(abc.ABCMeta, interfaces.Method)):
   """A controllable implementation of a stream-stream RPC method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, response_consumer, context, control):
     """Services an RPC that accepts and produces streams of messages.
@@ -244,11 +232,9 @@ class StreamStreamTestMethodImplementation(interfaces.Method):
     raise NotImplementedError()
 
 
-class StreamStreamTestMessages(object):
+class StreamStreamTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for stream-request-stream-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def requests(self):
     """Affords a sequence of request messages.
@@ -278,11 +264,9 @@ class StreamStreamTestMessages(object):
     raise NotImplementedError()
 
 
-class TestService(object):
+class TestService(six.with_metaclass(abc.ABCMeta)):
   """A specification of implemented RPC methods to use in tests."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def name(self):
     """Identifies the RPC service name used during the test.
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/test_case.py
index 23d4d919c2..5be9330a77 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/test_case.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,18 +31,19 @@
 
 import abc
 
+import six
+
 # face_interfaces and interfaces are referenced in specification in this module.
 from grpc.framework.face import interfaces as face_interfaces  # pylint: disable=unused-import
 from tests.unit.framework.face.testing import interfaces  # pylint: disable=unused-import
 
 
-class FaceTestCase(object):
+class FaceTestCase(six.with_metaclass(abc.ABCMeta)):
   """Describes a test of the Face Layer of RPC Framework.
 
   Concrete subclasses must also inherit from unittest.TestCase and from at least
   one class that defines test methods.
   """
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def set_up_implementation(
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/base/_control.py b/src/python/grpcio/tests/unit/framework/interfaces/base/_control.py
index 38102b198a..fe69e63995 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/base/_control.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/base/_control.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -36,6 +36,8 @@ import random  # pylint: disable=unused-import
 import threading
 import time
 
+import six
+
 from grpc.framework.interfaces.base import base
 from tests.unit.framework.common import test_constants
 from tests.unit.framework.interfaces.base import _sequence
@@ -247,8 +249,7 @@ class Instruction(
     CONCLUDE = 'CONCLUDE'
 
 
-class Controller(object):
-  __metaclass__ = abc.ABCMeta
+class Controller(six.with_metaclass(abc.ABCMeta)):
 
   @abc.abstractmethod
   def failed(self, message):
@@ -308,8 +309,7 @@ class Controller(object):
     raise NotImplementedError()
 
 
-class ControllerCreator(object):
-  __metaclass__ = abc.ABCMeta
+class ControllerCreator(six.with_metaclass(abc.ABCMeta)):
 
   @abc.abstractmethod
   def name(self):
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/base/test_interfaces.py b/src/python/grpcio/tests/unit/framework/interfaces/base/test_interfaces.py
index 84afd24d47..0594cfeb31 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/base/test_interfaces.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/base/test_interfaces.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,12 +31,13 @@
 
 import abc
 
+import six
+
 from grpc.framework.interfaces.base import base  # pylint: disable=unused-import
 
 
-class Serialization(object):
+class Serialization(six.with_metaclass(abc.ABCMeta)):
   """Specifies serialization and deserialization of test payloads."""
-  __metaclass__ = abc.ABCMeta
 
   def serialize_request(self, request):
     """Serializes a request value used in a test.
@@ -85,9 +86,8 @@ class Serialization(object):
     raise NotImplementedError()
 
 
-class Implementation(object):
+class Implementation(six.with_metaclass(abc.ABCMeta)):
   """Specifies an implementation of the Base layer."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def instantiate(self, serializations, servicer):
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
index c8a3a1bc74..a47fcd3681 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
@@ -34,6 +34,8 @@ import itertools
 import unittest
 from concurrent import futures
 
+import six
+
 # test_interfaces is referenced from specification in this module.
 from grpc.framework.foundation import logging_pool
 from grpc.framework.interfaces.face import face
@@ -46,14 +48,13 @@ from tests.unit.framework.interfaces.face import _stock_service
 from tests.unit.framework.interfaces.face import test_interfaces  # pylint: disable=unused-import
 
 
-class TestCase(test_coverage.Coverage, unittest.TestCase):
+class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.TestCase)):
   """A test of the Face layer of RPC Framework.
 
   Concrete subclasses must have an "implementation" attribute of type
   test_interfaces.Implementation and an "invoker_constructor" attribute of type
   _invocation.InvokerConstructor.
   """
-  __metaclass__ = abc.ABCMeta
 
   NAME = 'BlockingInvocationInlineServiceTest'
 
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
index 1d36a931e8..fb4bee6f86 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
@@ -36,6 +36,8 @@ import threading
 import unittest
 from concurrent import futures
 
+import six
+
 # test_interfaces is referenced from specification in this module.
 from grpc.framework.foundation import logging_pool
 from grpc.framework.interfaces.face import face
@@ -104,14 +106,13 @@ class _Callback(object):
           self._condition.wait()
 
 
-class TestCase(test_coverage.Coverage, unittest.TestCase):
+class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.TestCase)):
   """A test of the Face layer of RPC Framework.
 
   Concrete subclasses must have an "implementation" attribute of type
   test_interfaces.Implementation and an "invoker_constructor" attribute of type
   _invocation.InvokerConstructor.
   """
-  __metaclass__ = abc.ABCMeta
 
   NAME = 'FutureInvocationAsynchronousEventServiceTest'
 
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_invocation.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_invocation.py
index 448e845a08..ff38dc2ece 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_invocation.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_invocation.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
 
 import abc
 
+import six
+
 from grpc.framework.common import cardinality
 
 _CARDINALITY_TO_GENERIC_BLOCKING_BEHAVIOR = {
@@ -62,9 +64,8 @@ _CARDINALITY_TO_MULTI_CALLABLE_ATTRIBUTE = {
 }
 
 
-class Invoker(object):
+class Invoker(six.with_metaclass(abc.ABCMeta)):
   """A type used to invoke test RPCs."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def blocking(self, group, name):
@@ -82,9 +83,8 @@ class Invoker(object):
     raise NotImplementedError()
 
 
-class InvokerConstructor(object):
+class InvokerConstructor(six.with_metaclass(abc.ABCMeta)):
   """A type used to create Invokers."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def name(self):
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_service.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_service.py
index 28941e2ad0..bec8d5113c 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_service.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_service.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,16 +31,16 @@
 
 import abc
 
+import six
+
 # face is referenced from specification in this module.
 from grpc.framework.interfaces.face import face  # pylint: disable=unused-import
 from tests.unit.framework.interfaces.face import test_interfaces
 
 
-class UnaryUnaryTestMethodImplementation(test_interfaces.Method):
+class UnaryUnaryTestMethodImplementation(six.with_metaclass(abc.ABCMeta, test_interfaces.Method)):
   """A controllable implementation of a unary-unary method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, request, response_callback, context, control):
     """Services an RPC that accepts one message and produces one message.
@@ -59,11 +59,9 @@ class UnaryUnaryTestMethodImplementation(test_interfaces.Method):
     raise NotImplementedError()
 
 
-class UnaryUnaryTestMessages(object):
+class UnaryUnaryTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for unary-request-unary-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def request(self):
     """Affords a request message.
@@ -93,11 +91,9 @@ class UnaryUnaryTestMessages(object):
     raise NotImplementedError()
 
 
-class UnaryStreamTestMethodImplementation(test_interfaces.Method):
+class UnaryStreamTestMethodImplementation(six.with_metaclass(abc.ABCMeta, test_interfaces.Method)):
   """A controllable implementation of a unary-stream method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, request, response_consumer, context, control):
     """Services an RPC that takes one message and produces a stream of messages.
@@ -116,11 +112,9 @@ class UnaryStreamTestMethodImplementation(test_interfaces.Method):
     raise NotImplementedError()
 
 
-class UnaryStreamTestMessages(object):
+class UnaryStreamTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for unary-request-stream-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def request(self):
     """Affords a request message.
@@ -150,11 +144,9 @@ class UnaryStreamTestMessages(object):
     raise NotImplementedError()
 
 
-class StreamUnaryTestMethodImplementation(test_interfaces.Method):
+class StreamUnaryTestMethodImplementation(six.with_metaclass(abc.ABCMeta, test_interfaces.Method)):
   """A controllable implementation of a stream-unary method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, response_callback, context, control):
     """Services an RPC that takes a stream of messages and produces one message.
@@ -180,11 +172,9 @@ class StreamUnaryTestMethodImplementation(test_interfaces.Method):
     raise NotImplementedError()
 
 
-class StreamUnaryTestMessages(object):
+class StreamUnaryTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for stream-request-unary-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def requests(self):
     """Affords a sequence of request messages.
@@ -214,11 +204,9 @@ class StreamUnaryTestMessages(object):
     raise NotImplementedError()
 
 
-class StreamStreamTestMethodImplementation(test_interfaces.Method):
+class StreamStreamTestMethodImplementation(six.with_metaclass(abc.ABCMeta, test_interfaces.Method)):
   """A controllable implementation of a stream-stream method."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def service(self, response_consumer, context, control):
     """Services an RPC that accepts and produces streams of messages.
@@ -244,11 +232,9 @@ class StreamStreamTestMethodImplementation(test_interfaces.Method):
     raise NotImplementedError()
 
 
-class StreamStreamTestMessages(object):
+class StreamStreamTestMessages(six.with_metaclass(abc.ABCMeta)):
   """A type for stream-request-stream-response message pairings."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def requests(self):
     """Affords a sequence of request messages.
@@ -278,11 +264,9 @@ class StreamStreamTestMessages(object):
     raise NotImplementedError()
 
 
-class TestService(object):
+class TestService(six.with_metaclass(abc.ABCMeta)):
   """A specification of implemented methods to use in tests."""
 
-  __metaclass__ = abc.ABCMeta
-
   @abc.abstractmethod
   def unary_unary_scenarios(self):
     """Affords unary-request-unary-response test methods and their messages.
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/test_interfaces.py b/src/python/grpcio/tests/unit/framework/interfaces/face/test_interfaces.py
index b2b5c10fa6..a5e28b7942 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/test_interfaces.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/test_interfaces.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,13 +31,14 @@
 
 import abc
 
+import six
+
 from grpc.framework.common import cardinality  # pylint: disable=unused-import
 from grpc.framework.interfaces.face import face  # pylint: disable=unused-import
 
 
-class Method(object):
+class Method(six.with_metaclass(abc.ABCMeta)):
   """Specifies a method to be used in tests."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def group(self):
@@ -126,9 +127,8 @@ class Method(object):
     raise NotImplementedError()
 
 
-class Implementation(object):
+class Implementation(six.with_metaclass(abc.ABCMeta)):
   """Specifies an implementation of the Face layer."""
-  __metaclass__ = abc.ABCMeta
 
   @abc.abstractmethod
   def instantiate(
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/links/test_cases.py b/src/python/grpcio/tests/unit/framework/interfaces/links/test_cases.py
index dace6c23f3..2283e79f0a 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/links/test_cases.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/links/test_cases.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,6 +33,8 @@
 import abc
 import unittest  # pylint: disable=unused-import
 
+import six
+
 from grpc.framework.interfaces.links import links
 from tests.unit.framework.common import test_constants
 from tests.unit.framework.interfaces.links import test_utilities
@@ -58,13 +60,12 @@ _TRANSMISSION_GROUP = 'test.Group'
 _TRANSMISSION_METHOD = 'TestMethod'
 
 
-class TransmissionTest(object):
+class TransmissionTest(six.with_metaclass(abc.ABCMeta)):
   """Tests ticket transmission between two connected links.
 
   This class must be mixed into a unittest.TestCase that implements the abstract
   methods it provides.
   """
-  __metaclass__ = abc.ABCMeta
 
   # This is a unittest.TestCase mix-in.
   # pylint: disable=invalid-name