deploying to heroku I am facing this issue with laravel 5.8

remote: ! ERROR: Dependency installation failed!

remote: !

remote: ! The 'composer install' process failed with an error. The cause

remote: ! may be the download or installation of packages, or a pre- or

remote: ! post-install hook (e.g. a 'post-install-cmd' item in 'scripts')

remote: ! in your 'composer.json'.

remote: !

remote: ! Typical error cases are out-of-date or missing parts of code,

remote: ! timeouts when making external connections, or memory limits.

remote: !

remote: ! Check the above error output closely to determine the cause of

remote: ! the problem, ensure the code you're pushing is functioning

remote: ! properly, and that all local changes are committed correctly.

remote: !

remote: ! For more information on builds for PHP on Heroku, refer to

remote: ! https://devcenter.heroku.com/articles/php-support

remote: !

remote: ! REMINDER: the following warnings were emitted during the build;

remote: ! check the details above, as they may be related to this error:

remote: ! - Your 'composer.lock' is out of date!

remote: ! - Composer vendor dir found in project!

remote: ! - There was a class not found error in your code

remote:

remote: ! Push rejected, failed to compile PHP app.

remote:

remote: ! Push failed

remote: Verifying deploy...

remote:

remote: ! Push rejected to nameless-sierra-88678.

remote: