Update 4.3 fail! Deprecated problem

You could wait or else for temporary fix, you can hide the notice by adding define(‘WP_DEBUG’, false);
to your wp-config file.

Another thing is that I cannot save my post, do anything with the plugins.
I don’t think that hiding the notice will get me operate the dashboard as well.

The issue is either with the theme or any of plugin you are using.
Can you paste full error message?

Here is the complete message:
Notice: The called constructor method for WP_Widget is deprecated since version 4.3.0! Use
__construct()
instead. in /home/blessedl/public_html/wp-includes/functions.php on line 3457

Notice: The called constructor method for WP_Widget is deprecated since version 4.3.0! Use
__construct()
instead. in /home/blessedl/public_html/wp-includes/functions.php on line 3457

I use the genesis framework and have finished updating it.
Also with the plugins.
That’s why I retried update to 4.3
I wonder if I missed something to do.

Firstly, hiding the notice will work to allow you access to your dashboard again. You need to check your wp-config.php and make sure that WP_DEBUG is set to “false”. You also need to check with your PHP configuration and make sure that display_errors is NOT enabled. That is a development setting, it should never be enabled on a live site.

Second, the problem is not in WordPress 4.3, but in some plugin or theme you are using. The WP_Widget class is being called by some plugin or theme in an old and unsupported manner which will not work on future versions of PHP. The warning is there to tell the plugin or theme author to update their plugin code.

So you need to
a) Turn off debugging and error displays
b) Go to your dashboard, and
c) Update your plugins and/or themes.

Finally, I can upgrade my blog into 4.3. Thank you very much all!