Error displayed in wp-admin with debug enabled

Hi to all

I see an Error in the admin page every time I go to “Updates”.

Error occurred. Something may be wrong with ww.wp.xz.cn or this server’s configuration. If you continue to have problems, please try the support forums. (WordPress could not establish a secure connection to ww.wp.xz.cn. Please contact your server administrator.) in /var/www/html/wp-includes/update.php on line 123

The part “on line 123” changes sometimes with “476” or “306”.

This is a self-hosted website which have no content yet.

I’m using a web proxy (which I can control) and I have configured wp-config.php to use the proxy. I can update wordpress and plugins with no problem other that the displayed Error. And I also don’t see any error in the proxy logs.

I know that the Error would disappear if I disable DEBUG, but I want to be sure that everything is ok.

Site: www-test.fmorales.com

OS: Ubuntu 14.04 on LXC.

Web server: Apache 2.4.18

Thank you.