用npm安装spm出现如下错误：

系统环境：OS X Yosemite 10.10.5

npm ERR! Darwin 14.5.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install" "spm" "-g"
npm ERR! node v4.2.6
npm ERR! npm v2.14.12
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn

npm ERR! [email protected] install: node install.js
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the [email protected] install script 'node install.js'.
npm ERR! This is most likely a problem with the phantomjs package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR! node install.js
npm ERR! You can get their info via:
npm ERR! npm owner ls phantomjs
npm ERR! There is likely additional logging output above.

请问这是什么原因啊？