Allow custom template for database connection failure

[sbruner]

In the dead_db() function in wp-includes/functions.php, we allow for a custom template to load if the there is a db error. This same template could be used in db_connect().

[sbruner]

Screenshot of current error screen

[nacin]

Makes sense to me! Will check it out.

[kovshenin]

Should developers expect translations to be loaded before the db-error.php drop-in is included?

Because right now it depends on whether dead_db() is called in is_blog_installed() or in wp_set_wpdb_vars(), and db_connect() seems to suffer from the same issue with the proposed patch. Since we load translations anyway before displaying the default errors, I guess there's no problem in loading them for db-error.php.

See 25703.diff​

[wonderboymusic]

In 27056:

In wpdb::db_connect(), allow the loading of a custom database error template - this is already allowed in dead_db().

In dead_db(), move the call to wp_load_translations_early() before the inclusion of the db-error.php file to allow translation in both locations before the template is loaded.

Props sbruner, kovshenin.
Fixes #25703.

[nacin]

[27056] looks great.