Based on Magento 2.3 Documentation
This happens when your session.save_handler PHP parameter is set to some another session storage than files (for example, redis, memcached, and so on).
To solve it follow Magento suggestions :
1 - Upgrade Magento 2 Code
2 - Locate php.ini
php -i | grep "Loaded Configuration File"
As a user with root privileges, open php.ini in a text editor.
Locate session.save_handler
Set it in any of the following ways:
To comment it out:
;session.save_path = <path>
To set it to a file system path:
session.save_handler = files
3. Open app/etc/env.php
Change:
'session' =>
array (
'save' => 'files'
),
to
'session' =>
array (
'save' => 'db'
),