old_contents: # Licensed under the Apache License, Version 2.0 (the "License"); you may
  # not use this file except in compliance with the License. You may obtain
  # a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  # License for the specific language governing permissions and limitations
  # under the License.
  
  import argparse
  import os
  
  from keystoneclient.auth import base
  
  
  def register_argparse_arguments(parser, argv):
      """Register CLI options needed to create a plugin.
  
      The function inspects the provided arguments so that it can also register
      the options required for that specific plugin if available.
  
      :param argparse.ArgumentParser: the parser to attach argparse options to.
      :param list argv: the arguments provided to the appliation.
  
      :returns: The plugin class that will be loaded or None if not provided.
  
      :raises exceptions.NoMatchingPlugin: if a plugin cannot be created.
      """
      in_parser = argparse.ArgumentParser(add_help=False)
      env_plugin = os.environ.get('OS_AUTH_PLUGIN')
      for p in (in_parser, parser):
          p.add_argument('--os-auth-plugin',
                         metavar='<name>',
                         default=env_plugin,
                         help='The auth plugin to load')
  
      options, _args = in_parser.parse_known_args(argv)
      name = options.os_auth_plugin
  
      if not name:
          return None
  
      msg = 'Options specific to the %s plugin.' % name
      group = parser.add_argument_group('Authentication Options', msg)
  
      plugin = base.get_plugin_class(name)
      plugin.register_argparse_arguments(group)
      return plugin
  
  
  def load_from_argparse_arguments(namespace, **kwargs):
      """Retrieve the created plugin from the completed argparse results.
  
      Loads and creates the auth plugin from the information parsed from the
      command line by argparse.
  
      :param Namespace namespace: The result from CLI parsing.
  
      :returns: An auth plugin, or None if a name is not provided.
  
      :raises exceptions.NoMatchingPlugin: if a plugin cannot be created.
      """
      if not namespace.os_auth_plugin:
          return None
  
      plugin = base.get_plugin_class(namespace.os_auth_plugin)
      return plugin.load_from_argparse_arguments(namespace, **kwargs)
  
new_contents: # Licensed under the Apache License, Version 2.0 (the "License"); you may
  # not use this file except in compliance with the License. You may obtain
  # a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  # License for the specific language governing permissions and limitations
  # under the License.
  
  import argparse
  import os
  
  from keystoneclient.auth import base
  from keystoneclient import utils
  
  
  @utils.positional()
  def register_argparse_arguments(parser, argv, default=None):
      """Register CLI options needed to create a plugin.
  
      The function inspects the provided arguments so that it can also register
      the options required for that specific plugin if available.
  
      :param argparse.ArgumentParser: the parser to attach argparse options to.
      :param list argv: the arguments provided to the appliation.
      :param str/class default: a default plugin name or a plugin object to use
                                if one isn't specified by the CLI. default: None.
  
      :returns: The plugin class that will be loaded or None if not provided.
  
      :raises exceptions.NoMatchingPlugin: if a plugin cannot be created.
      """
      in_parser = argparse.ArgumentParser(add_help=False)
      env_plugin = os.environ.get('OS_AUTH_PLUGIN', default)
      for p in (in_parser, parser):
          p.add_argument('--os-auth-plugin',
                         metavar='<name>',
                         default=env_plugin,
                         help='The auth plugin to load')
  
      options, _args = in_parser.parse_known_args(argv)
  
      if not options.os_auth_plugin:
          return None
  
      if isinstance(options.os_auth_plugin, type):
          msg = 'Default Authentication options'
          plugin = options.os_auth_plugin
      else:
          msg = 'Options specific to the %s plugin.' % options.os_auth_plugin
          plugin = base.get_plugin_class(options.os_auth_plugin)
  
      group = parser.add_argument_group('Authentication Options', msg)
      plugin.register_argparse_arguments(group)
      return plugin
  
  
  def load_from_argparse_arguments(namespace, **kwargs):
      """Retrieve the created plugin from the completed argparse results.
  
      Loads and creates the auth plugin from the information parsed from the
      command line by argparse.
  
      :param Namespace namespace: The result from CLI parsing.
  
      :returns: An auth plugin, or None if a name is not provided.
  
      :raises exceptions.NoMatchingPlugin: if a plugin cannot be created.
      """
      if not namespace.os_auth_plugin:
          return None
  
      if isinstance(namespace.os_auth_plugin, type):
          plugin = namespace.os_auth_plugin
      else:
          plugin = base.get_plugin_class(namespace.os_auth_plugin)
  
      return plugin.load_from_argparse_arguments(namespace, **kwargs)
  
subject: Allow providing a default value to CLI loading