Dependency installation failed! error while deploying symfony app to heroku

remote: ! ERROR: Dependency installation failed!

remote: ! The 'composer install' process failed with an error. The cause may be the download or installation of packages, or a pre- or post-install hook (e.g. a 'post-install-cmd' item in 'scripts') in your 'composer.json'.

remote: ! Typical error cases are out-of-date or missing parts of code, timeouts when making external connections, or memory limits.

remote: ! Check the above error output closely to determine the cause of the problem, ensure the code you're pushing is functioning properly, and that all local changes are committed correctly. For more information on builds for PHP on Heroku, refer to

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

remote: ! Push failed remote: Verifying deploy...

remote: ! Push rejected to hidden-dawn-70674.