我做作曲家更新时遇到错误，它说RuntimeException
$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
- Removing mews/purifier (1.0.1)
[RuntimeException]
Could not delete /var/www/myproj.com/protected/vendor/mews/purifier/LICENCE.md:
update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-plugins] [--no-custom-installers] [--no-autoloader] [--no-scripts] [--no-progress] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [--ignore-platform-reqs] [--prefer-stable] [--prefer- lowest] [packages1] ... [packagesN]
有没有人对我的案子有所了解？