How to use the webob.exc.HTTPNotImplemented function in WebOb

def delete(self, req, server_id, id, **kwargs):
        """ Deletes an existing backup schedule """
        return faults.Fault(exc.HTTPNotImplemented())

context = req.environ['nova.context']
        authorize(context)
        try:
            hyp = self.host_api.compute_node_get(context, id)
            req.cache_db_compute_node(hyp)
        except (ValueError, exception.ComputeHostNotFound):
            msg = _("Hypervisor with ID '%s' could not be found.") % id
            raise webob.exc.HTTPNotFound(explanation=msg)

        # Get the uptime
        try:
            host = hyp.host
            uptime = self.host_api.get_host_uptime(context, host)
        except NotImplementedError:
            msg = _("Virt driver does not implement uptime function.")
            raise webob.exc.HTTPNotImplemented(explanation=msg)

        service = self.host_api.service_get_by_compute_host(context, host)
        return dict(hypervisor=self._view_hypervisor(hyp, service, False,
                                                     uptime=uptime))

def _host_power_action(self, req, host_name, action):
        """Reboots, shuts down or powers up the host."""
        context = req.environ['nova.context']
        authorize(context)
        # NOTE(alex_xu): back-compatible with db layer hard-code admin
        # permission checks. This has to be left only for API v2.0 because
        # this version has to be stable even if it means that only admins
        # can call this method while the policy could be changed.
        nova_context.require_admin_context(context)
        try:
            result = self.api.host_power_action(context, host_name=host_name,
                    action=action)
        except NotImplementedError:
            msg = _("Virt driver does not implement host power management.")
            raise webob.exc.HTTPNotImplemented(explanation=msg)
        except exception.NotFound as e:
            raise webob.exc.HTTPNotFound(explanation=e.format_message())
        except exception.ComputeServiceUnavailable as e:
            raise webob.exc.HTTPBadRequest(explanation=e.format_message())
        return {"host": host_name, "power_action": result}

def _dispatch(req):
        """
        Called by self._router after matching the incoming request to a route
        and putting the information into req.environ.  Either returns 404,
        501, or the routed WSGI app's response.
        """
        match = req.environ['wsgiorg.routing_args'][1]
        if not match:
            implemented_http_methods = ['GET', 'HEAD', 'POST', 'PUT',
                                        'DELETE', 'PATCH']
            if req.environ['REQUEST_METHOD'] not in implemented_http_methods:
                return webob.exc.HTTPNotImplemented()
            else:
                return webob.exc.HTTPNotFound()
        app = match['controller']
        return app

def _check_ironic_client_enabled():
    """Check whether Ironic is installed or not."""
    if ironic_client is None:
        msg = _("Ironic client unavailable, cannot access Ironic.")
        raise webob.exc.HTTPNotImplemented(explanation=msg)

return webob.Response(status=status, headers=headers,
                                      app_iter=app_iter)(env, start_response)
            elif status == 404:
                # only send thumbs to the 404 handler; just return a 404 for everything else.
                if repo == 'local' and zone == 'thumb':
                    resp = self.handle404(reqorig, url, container, obj)
                    return resp(env, start_response)
                else:
                    resp = webob.exc.HTTPNotFound('File not found: %s' % req.path)
                    return resp(env, start_response)
            elif status == 401:
                # if the Storage URL is invalid or has expired we'll get this error.
                resp = webob.exc.HTTPUnauthorized('Token may have timed out')
                return resp(env, start_response)
            else:
                resp = webob.exc.HTTPNotImplemented('Unknown Status: %s' % (status))
                return resp(env, start_response)
        else:
            resp = webob.exc.HTTPNotFound('Regexp failed to match URI: "%s"' % (req.path))
            return resp(env, start_response)

def __call__(self, environ, start_response):
        """Called by WSGI when a request comes in.

        :param environ:
            A WSGI environment.
        :param start_response:
            A callable accepting a status code, a list of headers and an
            optional exception context to start the response.
        :returns:
            An iterable with the response to return to the client.
        """
        with self.request_context_class(self, environ) as (request, response):
            try:
                if request.method not in self.allowed_methods:
                    # 501 Not Implemented.
                    raise exc.HTTPNotImplemented()

                rv = self.router.dispatch(request, response)
                if rv is not None:
                    response = rv
            except Exception, e:
                try:
                    # Try to handle it with a custom error handler.
                    rv = self.handle_exception(request, response, e)
                    if rv is not None:
                        response = rv
                except HTTPException, e:
                    # Use the HTTP exception as response.
                    response = e
                except Exception, e:
                    # Error wasn't handled so we have nothing else to do.
                    response = self._internal_error(e)

def __call__(self, environ, start_response):
        """Called by WSGI when a request comes in.

        :param environ:
            A WSGI environment.
        :param start_response:
            A callable accepting a status code, a list of headers and an
            optional exception context to start the response.
        :returns:
            An iterable with the response to return to the client.
        """
        with self.request_context_class(self, environ) as (request, response):
            try:
                if request.method not in self.allowed_methods:
                    # 501 Not Implemented.
                    raise exc.HTTPNotImplemented()

                rv = self.router.dispatch(request, response)
                if rv is not None:
                    response = rv
            except Exception, e:
                try:
                    # Try to handle it with a custom error handler.
                    rv = self.handle_exception(request, response, e)
                    if rv is not None:
                        response = rv
                except HTTPException, e:
                    # Use the HTTP exception as response.
                    response = e
                except Exception, e:
                    # Error wasn't handled so we have nothing else to do.
                    response = self._internal_error(e)

def _set_enabled_status(self, context, host_name, enabled):
        """Sets the specified host's ability to accept new instances.

        :param enabled: a boolean - if False no new VMs will be able to start
        on the host
        """
        if enabled:
            LOG.info(_LI("Enabling host %s.") % host_name)
        else:
            LOG.info(_LI("Disabling host %s.") % host_name)
        try:
            result = self.api.set_host_enabled(context, host_name=host_name,
                    enabled=enabled)
        except NotImplementedError:
            msg = _("Virt driver does not implement host disabled status.")
            raise webob.exc.HTTPNotImplemented(explanation=msg)
        except exception.NotFound as e:
            raise webob.exc.HTTPNotFound(explanation=e.format_message())
        except exception.ComputeServiceUnavailable as e:
            raise webob.exc.HTTPBadRequest(explanation=e.format_message())
        if result not in ("enabled", "disabled"):
            raise webob.exc.HTTPBadRequest(explanation=result)
        return result