Odd hint at the end of update progress #13993

It appears you have executed this update with user root:root, while your Matomo files are owned by www-data:www-data. 

To ensure that the Matomo files are readable by the correct user, you may need to run the following command (or a similar command depending on your server configuration):

$ chown -R root:root /var/www/piwik

Shouldn't that be chown -R 33:33 /var/www/piwik?