显然，Google App Engine for WordPress插件必须在Wordpress的本地副本中停用。仍然有必要在App Engine的产品副本中激活它。

When I try to update plugins in the local copy of Wordpress for App Engine, I see the following error:

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

The only reference to this error message that I could find comes from 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.'));
    }

I know that I can simply add plugin files manually, but it would be nice to do it with a single click on the "Update" link. Does anyone know how to avoid this error?

I am using Mac OS 10.7.

Apparently, Google App Engine for WordPress plugin must be deactivated in a local copy of Wordpress. It is still necessary to activate it in a production copy on App Engine.