josephmouhanna on "Updating to 4.4.2 I am getting a 500 server error"

I updated my installation to 4.4.2 (I believe it was 4.4.1) and now I am getting a 500 error.

This is on an Ubuntu 14.04 server. The CustomLog file says:

"GET / HTTP/1.1" 500 206 "-" "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:44.0) Gecko/20100101 Firefox/44.0"
"POST /wp-cron.php?doing_wp_cron=1455771197.6090118885040283203125 HTTP/1.0" 500 206 "-" "WordPress/4.4.2; http://xxxxxxxxxxxxxxxxxx.com"

and there is nothing in the php error file

Any ideas?