Here is the error I am getting:
Script php artisan optimize handling the post-update-cmd event returned with an error
[RuntimeException]
Error Output:
up
It looks like your laravel install did not run correctly and since part of the composer.json runs the php artisan clear-compiled and php artisan optimize if your laravel application is not working then composer will fail.
Try running your composer update without invoking the Laravel scripts.
php composer update --no-scripts
After that you can either run the commands from the scripts block in your composer.json manually. Else you can just run a standard
php composer update
again which will run the scripts for you.