Fix the policy argument in server-group-create

In the "server-group-create" command, multiple policies
can be specified currently. But only one item is allowed
in the nova side. So make the command allow only one policy.

Change-Id: Ifd2d084faa2b849d6ee466d9accbad21b6a4e11b
Closes-Bug: #1767287

novaclient/tests/unit/v2/test_shell.py

@@ -3571,6 +3571,10 @@ class ShellTest(utils.TestCase):
                            {'server_group': {'name': 'wjsg',
                                              'policies': ['affinity']}})
 
+    def test_create_server_group_with_multiple_policies(self):
+        self.assertRaises(SystemExit, self.run_command,
+                          'server-group-create wjsg affinity anti-affinity')
+
     def test_delete_multi_server_groups(self):
         self.run_command('server-group-delete 12345 56789')
         self.assert_called('DELETE', '/os-server-groups/56789')

novaclient/v2/shell.py

@@ -4501,8 +4501,7 @@ def do_server_group_list(cs, args):
 @utils.arg(
     'policy',
     metavar='<policy>',
-    nargs='+',
-    help=_('Policies for the server groups.'))
+    help=_('Policy for the server group.'))
 def do_server_group_create(cs, args):
     """Create a new server group with the specified details."""
     server_group = cs.server_groups.create(name=args.name,

releasenotes/notes/bug-1767287-cc28d60d9e59f9bd.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    The ``nova server-group-create`` command now only supports specifying
+    a single policy name when creating the server group. This is to match
+    the server-side API validation.