Loads custom DB error or display WordPress DB error.

If a file exists in the wp-content directory named db-error.php, then it will
be loaded instead of displaying the WordPress DB error. If it is not found,
then the WordPress DB error will be displayed instead.

The WordPress DB error sets the HTTP status header to 500 to try to prevent
search engines from caching the message. Custom DB messages should do the
same.

This function was backported to WordPress 2.3.2, but originally was added
in WordPress 2.5.0.

function dead_db() {
	global $wpdb;

	wp_load_translations_early();

	// Load custom DB error template, if present.
	if ( file_exists( WP_CONTENT_DIR . '/db-error.php' ) ) {
		require_once WP_CONTENT_DIR . '/db-error.php';
		die();
	}

	// If installing or in the admin, provide the verbose message.
	if ( wp_installing() || defined( 'WP_ADMIN' ) ) {
		wp_die( $wpdb->error );
	}

	// Otherwise, be terse.
	wp_die( '
' . __( 'Error establishing a database connection' ) . '
', __( 'Database Error' ) );
}