Use public discover_extensions from novaclient

_discover_extensions is moved to novaclient.client.discover_extensions,
and _discover_extensions will be removed from novaclient once this
patch get merged. Using the public discover_extensions instead of
_discover_extensions.

Change-Id: Id403a8313155f6ceabfdda626cdc79d9f0fac0d1
Closes-bug: #1440779

heat/engine/clients/os/nova.py

@@ -22,7 +22,6 @@ import string
 
 from novaclient import client as nc
 from novaclient import exceptions
-from novaclient import shell as novashell
 from oslo_config import cfg
 from oslo_serialization import jsonutils
 from oslo_utils import uuidutils
@@ -65,8 +64,16 @@ class NovaClientPlugin(client_plugin.ClientPlugin):
         management_url = self.url_for(service_type=self.service_types[0],
                                       endpoint_type=endpoint_type)
 
-        computeshell = novashell.OpenStackComputeShell()
-        extensions = computeshell._discover_extensions(NOVACLIENT_VERSION)
+        if hasattr(nc, 'discover_extensions'):
+            extensions = nc.discover_extensions(NOVACLIENT_VERSION)
+        else:
+            # TODO(lyj): The else condition is for backward compatibility,
+            #            once novaclient bump to a newer version with
+            #            discover_extensions exists, this should be safely
+            #            removed.
+            from novaclient import shell as novashell
+            computeshell = novashell.OpenStackComputeShell()
+            extensions = computeshell._discover_extensions(NOVACLIENT_VERSION)
 
         args = {
             'project_id': self.context.tenant,

heat/tests/test_nova_client.py

@@ -16,6 +16,7 @@ import collections
 import uuid
 
 import mock
+from novaclient import client as nc
 from novaclient import exceptions as nova_exceptions
 from oslo_config import cfg
 import six
@@ -44,6 +45,13 @@ class NovaClientPluginTests(NovaClientPluginTestCase):
     :module:'heat.engine.clients.os.nova'.
     """
 
+    def test_create(self):
+        self.nova_plugin._get_client_option = mock.MagicMock()
+        self.nova_plugin.url_for = mock.MagicMock()
+        nc.discover_extensions = mock.MagicMock()
+        self.nova_plugin._create()
+        nc.discover_extensions.assert_called_once_with('2')
+
     def test_get_ip(self):
         my_image = mock.MagicMock()
         my_image.addresses = {