enable barbican help without authentication

This fix enables 'barbican help' and 'barbican complete' to
not need authentication. This commit also enables deferred_help
so that the following command can be ran:
'barbican secret list --help' (the help for the
particular command will be shown).
The code changes are similar to the python-openstackclient
usage of the cliff library. The current implementation
of the barbican client authenticates before checking the type of
command. This early authentication causes the client
to fail with 'barbican help'. This code change will
check if the command requires authentication
and creates the client.

Change-Id: If335ef0373c75b145dc696d8501153da59fff1b7
Closes-Bug: #1488934

barbicanclient/barbican.py

@@ -20,7 +20,10 @@ Command-line interface to the Barbican API.
 import sys
 
 from cliff import app
+from cliff import command
 from cliff import commandmanager
+from cliff import complete
+from cliff import help
 from keystoneclient.auth.identity import v3
 from keystoneclient.auth.identity import v2
 from keystoneclient import session
@@ -37,10 +40,20 @@ class Barbican(app.App):
     """Barbican command line interface."""
 
     def __init__(self, **kwargs):
+        self.client = None
+
+        # Patch command.Command to add a default auth_required = True
+        command.Command.auth_required = True
+
+        # Some commands do not need authentication
+        help.HelpCommand.auth_required = False
+        complete.CompleteCommand.auth_required = False
+
         super(Barbican, self).__init__(
             description=__doc__.strip(),
             version=version.__version__,
             command_manager=commandmanager.CommandManager('barbican.client'),
+            deferred_help=True,
             **kwargs
         )
 
@@ -290,14 +303,14 @@ class Barbican(app.App):
         session.Session.register_cli_options(parser)
         return parser
 
-    def initialize_app(self, argv):
-        """Initializes the application.
-        Checks if the minimal parameters are provided and creates the client
-        interface.
+    def prepare_to_run_command(self, cmd):
+        """Prepares to run the command
+        Checks if the minimal parameters are provided and creates the
+        client interface.
         This is inherited from the framework.
         """
-        args = self.options
-        self.client = self.create_client(args)
+        if cmd.auth_required:
+            self.client = self.create_client(self.options)
 
     def run(self, argv):
         # If no arguments are provided, usage is displayed

barbicanclient/tests/test_barbican.py

@@ -48,7 +48,7 @@ class WhenTestingBarbicanCLI(test_client.BaseEntityResource):
         return client
 
     def test_should_show_usage_with_help_flag(self):
-        e = self.assertRaises(SystemExit, self.parser.parse_known_args, ['-h'])
+        e = self.assertRaises(SystemExit, self.barbican.run, ['-h'])
         self.assertEqual(0, e.code)
         self.assertIn('usage', self.captured_stdout.getvalue())