'policy' should be required in server_group_create

The 'policies' param is a required param in nova api now.
So, we also need to change it in cli.

After the modification, the 'policy' param will be required now,
and the old '--policy' style will still be available.

Change-Id: I97921eef0f635c8d50a04bbdaf3ef4f1bfaa3e9d
Closes-Bug: #1323909

novaclient/tests/v1_1/test_shell.py

@@ -2027,6 +2027,13 @@ class ShellTest(utils.TestCase):
         self.run_command('keypair-delete test')
         self.assert_called('DELETE', '/os-keypairs/test')
 
+    def test_create_server_group(self):
+        self.run_command('server-group-create wjsg affinity')
+        self.assert_called('POST', '/os-server-groups',
+                           {'server_group':
+                              {'name': 'wjsg',
+                               'policies': ['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/v1_1/shell.py

@@ -3572,13 +3572,33 @@ def do_server_group_list(cs, args):
 
 
 @utils.arg('name', metavar='<name>', help='Server group name.')
-@utils.arg('--policy', metavar='<policy>', action='append',
-           dest='policies', default=[], type=str,
-           help='Policies for the server groups')
+# NOTE(wingwj): The '--policy' way is still reserved here for preserving
+# the backwards compatibility of CLI, even if a user won't get this usage
+# in '--help' description. It will be deprecated after an suitable deprecation
+# period(probably 2 coordinated releases or so).
+#
+# Moreover, we imagine that a given user will use only positional parameters or
+# only the "--policy" option. So we don't need to properly handle
+# the possibility that they might mix them here. That usage is unsupported.
+# The related discussion can be found in
+# https://review.openstack.org/#/c/96382/2/.
+@utils.arg('policy',
+           metavar='<policy>',
+           default=argparse.SUPPRESS,
+           nargs='*',
+           help='Policies for the server groups '
+            '("affinity" or "anti-affinity")')
+@utils.arg('--policy',
+           default=[],
+           action='append',
+           help=argparse.SUPPRESS)
 def do_server_group_create(cs, args):
     """Create a new server group with the specified details."""
+    if not args.policy:
+        raise exceptions.CommandError(_("at least one policy must be "
+                                        "specified"))
     kwargs = {'name': args.name,
-              'policies': args.policies}
+              'policies': args.policy}
     server_group = cs.server_groups.create(**kwargs)
     _print_server_group_details([server_group])