Comment 9 for bug 1313266

To add more information, the CLI way to list them is as mentioned 'nova list-extensions':

http://docs.openstack.org/user-guide/content/novaclient_commands.html#novaclient_subcommand_list-extensions

and the client way looks like this:

from novaclient import extension
from novaclient.v1_1 import client
from novaclient.v1_1.contrib import list_extensions

extensions = [extension.Extension('list_extensions', list_extensions)]
c = client.Client('admin', 'a', 'admin', auth_url='http://localhost:5000/v2.0', extensions=extensions)
c.list_extensions.show_all()