奇怪的错误

连接packagist 没问题，但是很慢，有时候超时。
连接国内的镜像，直接报错。

vagrant@homestead:~/Code/testla$ composer update --dry-run --profile
[7.5MB/0.21s] Loading composer repositories with package information

  [ErrorException]                         
  Invalid argument supplied for foreach()  

update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-plugins] [--no-custom-installers] [--no-scripts] [--no-progress] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [--ignore-platform-reqs] [packages1] ... [packagesN]