Merge pull request #22549 from gnossen/simple_stubs_3_6_and_up

Add version check for Python 3.6 to simple stubs

src/python/grpcio/grpc/experimental/__init__.py

@@ -85,6 +85,6 @@ __all__ = (
     'insecure_channel_credentials',
 )
 
-if sys.version_info[0] >= 3:
+if sys.version_info[0] == 3 and sys.version_info[1] >= 6:
     from grpc._simple_stubs import unary_unary, unary_stream, stream_unary, stream_stream
     __all__ = __all__ + (unary_unary, unary_stream, stream_unary, stream_stream)

src/python/grpcio_tests/tests/protoc_plugin/_python_plugin_test.py

@@ -504,7 +504,8 @@ class PythonPluginTest(unittest.TestCase):
         service.server.stop(None)
 
 
-@unittest.skipIf(sys.version_info[0] < 3, "Unsupported on Python 2.")
+@unittest.skipIf(sys.version_info[0] < 3 or sys.version_info[1] < 6,
+                 "Unsupported on Python 2.")
 class SimpleStubsPluginTest(unittest.TestCase):
     servicer_methods = _ServicerMethods()