Extension check during upgrade does not work on WordPress prior to 5.1

[johnbillion]

As discovered by the upgrade checks for 6.8 beta 1, the check for missing required extensions during the upgrade process that were added in [59803] calls the WP_Error::has_errors() method which was introduced in WordPress 5.1. This means sites running WordPress prior to 5.1 will experience a fatal during the upgrade process.

The site will remain online and functional, but it won't be possible to proceed with the upgrade.

Example failing workflow: ​https://github.com/WordPress/wordpress-develop/actions/runs/13657290367/job/38180581900

Trac ticket: https://core.trac.wordpress.org/ticket/63052

I've added a develop upgrade check for WordPress 5.0 too, but we might need to exclude this from running on PHP 8.4. Let's see what the tests tell us.

[swissspidy]

This error causes some WP-CLI tests to fail too, see ​https://github.com/wp-cli/core-command/actions/runs/13743595251/job/38436006640#step:11:135

[johnbillion]

In 59956:

Upgrade/Install: Adjust the check for missing extensions during an upgrade so it remains compatible with versions of WordPress prior to 5.1.

The WP_Error::has_errors() method was introduced in WordPress 5.1, so this change uses its internal logic instead to remain compatible with earlier versions.

Props swissspidy, joemcgill, desrosj.

Fixes #63052