[InvalidArgumentException]
  Version "composer" could not be found.
  [Composer\Downloader\TransportException]
  The "https://getcomposer.org/download/composer/composer.phar.sig" file could not be downloaded (HTTP/2 404 )
    //use this command inorder to fix above error
    config -g repo.packagist composer https://packagist.phpcomposer.com