code: public function changePasswordAction()
      {
          $user = $this->getUser();
          if (!is_object($user) || !$user instanceof UserInterface) {
              $this->createAccessDeniedException('This user does not have access to this section.');
          }
          $form = $this->get('fos_user.change_password.form');
          $formHandler = $this->get('fos_user.change_password.form.handler');
          $process = $formHandler->process($user);
          if ($process) {
              $this->setFlash('fos_user_success', 'change_password.flash.success');
              return $this->redirect($this->getRedirectionUrl($user));
          }
          return $this->render(
              'SonataUserBundle:ChangePassword:changePassword.html.' . $this->container->getParameter('fos_user.template.engine'),
              array('form' => $form->createView())
          );
      }
docs: @return Response|RedirectResponse
  
  @throws AccessDeniedException