Warning (2): Use of undefined constant LANGUAGE - assumed 'LANGUAGE' (this will throw an Error in a future version of PHP) [APP/Controller/AppController.php, line 356]
Warning (2): Use of undefined constant CODE_TEMPLATE - assumed 'CODE_TEMPLATE' (this will throw an Error in a future version of PHP) [APP/Model/Table/TemplatesPageTable.php, line 38]
Warning (2): Use of undefined constant CODE_TEMPLATE - assumed 'CODE_TEMPLATE' (this will throw an Error in a future version of PHP) [APP/Model/Table/TemplatesPageTable.php, line 56]
Warning (512): Unable to emit headers. Headers sent in file=/home/core_v5/vendor/cakephp/cakephp/src/Error/Debugger.php line=841 [CORE/src/Http/ResponseEmitter.php, line 71]
Warning (2): Cannot modify header information - headers already sent by (output started at /home/core_v5/vendor/cakephp/cakephp/src/Error/Debugger.php:841) [CORE/src/Http/ResponseEmitter.php, line 168]
Warning (2): Cannot modify header information - headers already sent by (output started at /home/core_v5/vendor/cakephp/cakephp/src/Error/Debugger.php:841) [CORE/src/Http/ResponseEmitter.php, line 197]
Error: Connection to Mysql could not be established: SQLSTATE[HY000] [2002] Connection refused

Connection to Mysql could not be established: SQLSTATE[HY000] [2002] Connection refused 📋

Cake\Database\Exception\MissingConnectionException
Toggle Vendor Stack Frames
/home/core_v5/vendor/cakephp/cakephp/src/Database/Driver.php Toggle Arguments
                $config['password'] ?: null,
                $config['flags']
            );
        } catch (PDOException $e) {
            throw new MissingConnectionException(
                [
                    'driver' => App::shortName(static::class, 'Database/Driver'),
                    'reason' => $e->getMessage(),
                ],

If you want to customize this error message, create templates/Error/error500.php