Laravel Error - No supported encrypter found. The cipher and / or key length are invalid.

While running  composer install or php artisan optimize, If you get this error, here is the solution.

Solution :

Change values in config/app.php

'cipher' => 'AES-256-CBC',
to
'cipher' => MCRYPT_RIJNDAEL_128,

Now run again composer install or php artisan optimize , you will not get the same error again.