[Composer\Downloader\TransportException]
The "https://packagist.phpcomposer.com/p/provider-2019-01%241083636756831bc6ca0a7b15a464cb6375f4a25e56edf670c6c3e3ad02f33000.j
son" file could not be downloaded (HTTP/1.1 404 Not Found)
解决办法：composer config -g repo.packagist composer https://packagist.laravel-china.org。更换镜像源。