Petr, can you add a screen to the upgrade process (or combine it on the first screen) in admin/index.php so that it prints the current environment table with all details about compliance etc.

If there are no problems, there are just [Continue with upgrade] and [Cancel] buttons.

If there are problems it says "Your server does not meet the requirements for this version" and there are [Upgrade anyway] and [Cancel Upgrade].

This would prevent a lot of people getting into trouble by trying to upgrade with old MySQL etc.