To get sphinx autodoc work I add to the conf.py a path to the project directory and a path to the GAE SDK which contain some required libraries:
# todo: Please specify `gae_path' below (a path to the google app
# engine SDK directory)
gae_path = '~/google_appengine'
gae_path = os.path.expanduser(gae_path)
sys.path.insert(0, os.path.abspath('../'))
sys.path.insert(0, os.path.abspath(gae_path))
sys.path.insert(0, os.path.abspath(os.path.join(gae_path, 'lib/yaml/lib')))
sys.path.insert(0, os.path.abspath(os.path.join(gae_path, 'lib/webapp2')))
sys.path.insert(0, os.path.abspath(os.path.join(gae_path, 'lib/webob_1_1_1')))
logging.debug('sys.path: %s', sys.path)