HTMLPurifier 下载失败？

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vagrant@homestead:~/Code/LaraBBS$ composer require "mews/purifier:~2.0"
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 2 installs, 0 updates, 0 removals

• Installing ezyang/htmlpurifier (v4.10.0): Downloading (100%)
  proc_open(): fork failed - Cannot allocate memory
  The archive may contain identical file names with different capitalization (which fails on case insensitive filesystems)
  Unzip with unzip command failed, falling back to ZipArchive class
  The following exception is caused by a lack of memory or swap, or not having swap configured
  Check https://getcomposer.org/doc/articles/troub... for details

  [ErrorException]
  proc_open(): fork failed - Cannot allocate memory

require [--dev] [--prefer-source] [--prefer-dist] [--no-progress] [--no-suggest] [--no-update] [--no-scripts] [--update-no-dev] [--update-with-dependencies] [--update-with-all-dependencies] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [--sort-packages] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--] []...

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