Problem deploying to Heroku

Hi all,

Im trying to deploy my app to Heroku but when I do the push I get this error:

...
remote: -----> Preparing runtime environment...
remote: ln: failed to create symbolic link ‘./heroku-hhvm-apache2’: File exists
remote: ln: failed to create symbolic link ‘./heroku-hhvm-nginx’: File exists
remote: ln: failed to create symbolic link ‘./heroku-php-apache2’: File exists
remote: ln: failed to create symbolic link ‘./heroku-php-nginx’: File exists
remote: 
remote:  !     Push rejected, failed to compile Multipack app
remote: 
remote: Verifying deploy....
remote: 
remote: !   Push rejected to studapp-stage.
remote: 
To git@heroku.com:studapp-stage.git
 ! [remote rejected] studapp_laravel -> master (pre-receive hook declined)
error: failed to push some refs to 'git@heroku.com:studapp-stage.git'

I read something about the composer.lock file. I deleted the vendor folder, I made the composer update/install and the error still persist.

Can someone help me?

Thanks in advance!