fatal error by upgrading to WordPress 4.7 from 4.6

[websitenum1]

fatal error by upgrading to WordPress 4.7
thanks in advance

​http://websitenum1.ga/

Fatal error: Uncaught Error: Class 'WP_Taxonomy' not found in /home/_/public_html/wp-includes/taxonomy.php:384 Stack trace: #0 /home/_/public_html/wp-includes/taxonomy.php(72): register_taxonomy('category', 'post', Array) #1 /home/_/public_html/wp-settings.php(264): create_initial_taxonomies() #2 /home/_/public_html/wp-config.php(101): require_once('/home/_...') #3 /home/_/public_html/wp-load.php(39): require_once('/home/_...') #4 /home/_/public_html/wp-blog-header.php(13): require_once('/home/_...') #5 /home/_/public_html/index.php(17): require('/home/u56211230...') #6 {main} thrown in /home/_/public_html/wp-includes/taxonomy.php on line 384

[programmin]

This is preceded by a 'session.php is <strong>deprecated</strong> since version 4.7.0 with no alternative available.'

Then it gets that fatal WP_Taxonomy not found.

If you search for this you'll see that a bunch of random websites are getting these two error messages in that order: ​https://duckduckgo.com/?q=session.php+is+deprecated+since+version+4.7.0&t=canonical&ia=web

[dd32]

This appears to be caused by either
a) A bad update - wp-includes/taxonomy.php / wp-includes/version.php updated but wp-settings.php didn't
or
b) A bad plugin - which includes wp-includes/session.php & wp-includes/taxonomy.php but not their dependencies before WordPress is fully loaded.

It's much more likely that these have been caused by failed updates IMHO, rather than a plugin, seems like an odd thing for a plugin to do - I can't rule it out though.
This would be a very common failure in the event that wp-settings.php didn't get updated, or the wp-includes/class-wp-taxonomy.php file didn't get created, as it's the first real piece of code which runs which has dependancies upon new files.

Unfortunately update issues are going to happen occasionally, and I don't see anything we can do here.

@websitenum1 Were you able to do any debugging of your site to determine the cause of your problems? I note that it's currently running WordPress 4.7.1

[programmin]

Actually I can confirm that renaming each plugin in wp-content/plugins (disabling them), and re-installing Wordpress by overwriting all but wp-content, does not immediately fix it. Site seems fine now though.

[boonebgorges]

It appears that this was due to an incomplete update rather than a bug in WordPress. As such, I think we can close.