如何更新Wordpress for App Engine的本地副本中的Wordpress插件？

当我尝试更新Wordpress for App Engine的本地副本中的插件时,我看到以下错误:

Downloading update from https://downloads.wordpress.org/plugin/batcache.1.2.zip…
Download failed. Saving to a file is not currently supported.

我能找到的唯一对此错误消息的引用来自appengine-wordpress-plugin/modules/urlfetch.php:

// For now, lets not support streaming into a file and see what breaks
    if (isset($r['filename'])) {
      return new WP_Error( 'http_request_failed',
          __( 'Saving to a file is not currently supported.'));
    }

我知道我可以手动添加插件文件,但只需单击"更新"链接就可以了.有谁知道如何避免这个错误？

我使用的是Mac OS 10.7.