安装ElementUI主题生成工具一直报错，貌似是node-sass的问题，但是网上所有方法都试过了还是解决不了，是不是不是node-sass的问题而是其他原因？
报错信息：

liangyuefangdeMacBook-Pro:knowledge-platform liangyuefang$ sudo npm i element-theme -g
Password:
npm WARN deprecated gulp-util@3.0.8: gulp-util is deprecated - replace it, following the guidelines at https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5
npm WARN deprecated graceful-fs@3.0.11: please upgrade to graceful-fs 4 for compatibility with current and future versions of Node.js
npm WARN deprecated minimatch@2.0.10: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated minimatch@0.2.14: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated graceful-fs@1.2.3: please upgrade to graceful-fs 4 for compatibility with current and future versions of Node.js
npm WARN deprecated natives@1.1.2: This module relies on Node.js's internals and will break at some point. Do not use it, and update to graceful-fs@4.x.
npm WARN deprecated gulp-util@2.2.20: gulp-util is deprecated - replace it, following the guidelines at https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5
npm WARN deprecated graceful-fs@2.0.3: please upgrade to graceful-fs 4 for compatibility with current and future versions of Node.js
/usr/local/bin/et -> /usr/local/lib/node_modules/element-theme/bin/element-theme
/usr/local/bin/element-theme -> /usr/local/lib/node_modules/element-theme/bin/element-theme

> node-sass@4.8.3 install /usr/local/lib/node_modules/element-theme/node_modules/node-sass
> node scripts/install.js

Unable to save binary /usr/local/lib/node_modules/element-theme/node_modules/node-sass/vendor/darwin-x64-57 : { Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/element-theme/node_modules/node-sass/vendor'
    at Object.fs.mkdirSync (fs.js:885:18)
    at sync (/usr/local/lib/node_modules/element-theme/node_modules/mkdirp/index.js:71:13)
    at Function.sync (/usr/local/lib/node_modules/element-theme/node_modules/mkdirp/index.js:77:24)
    at checkAndDownloadBinary (/usr/local/lib/node_modules/element-theme/node_modules/node-sass/scripts/install.js:114:11)
    at Object.<anonymous> (/usr/local/lib/node_modules/element-theme/node_modules/node-sass/scripts/install.js:157:1)
    at Module._compile (module.js:635:30)
    at Object.Module._extensions..js (module.js:646:10)
    at Module.load (module.js:554:32)
    at tryModuleLoad (module.js:497:12)
    at Function.Module._load (module.js:489:3)
  errno: -13,
  code: 'EACCES',
  syscall: 'mkdir',
  path: '/usr/local/lib/node_modules/element-theme/node_modules/node-sass/vendor' }

> node-sass@4.8.3 postinstall /usr/local/lib/node_modules/element-theme/node_modules/node-sass
> node scripts/build.js

Building: /usr/local/bin/node /usr/local/lib/node_modules/element-theme/node_modules/node-gyp/bin/node-gyp.js rebuild --verbose --libsass_ext= --libsass_cflags= --libsass_ldflags= --libsass_library=
gyp info it worked if it ends with ok
gyp verb cli [ '/usr/local/bin/node',
gyp verb cli   '/usr/local/lib/node_modules/element-theme/node_modules/node-gyp/bin/node-gyp.js',
gyp verb cli   'rebuild',
gyp verb cli   '--verbose',
gyp verb cli   '--libsass_ext=',
gyp verb cli   '--libsass_cflags=',
gyp verb cli   '--libsass_ldflags=',
gyp verb cli   '--libsass_library=' ]
gyp info using node-gyp@3.6.2
gyp info using node@8.9.3 | darwin | x64
gyp verb command rebuild []
gyp verb command clean []
gyp verb clean removing "build" directory
gyp verb command configure []
gyp verb check python checking for Python executable "python2" in the PATH
gyp verb `which` failed Error: not found: python2
gyp verb `which` failed     at getNotFoundError (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:13:12)
gyp verb `which` failed     at F (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:68:19)
gyp verb `which` failed     at E (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:80:29)
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/which/which.js:89:16
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/isexe/index.js:42:5
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/isexe/mode.js:8:5
gyp verb `which` failed     at FSReqWrap.oncomplete (fs.js:152:21)
gyp verb `which` failed  python2 { Error: not found: python2
gyp verb `which` failed     at getNotFoundError (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:13:12)
gyp verb `which` failed     at F (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:68:19)
gyp verb `which` failed     at E (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:80:29)
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/which/which.js:89:16
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/isexe/index.js:42:5
gyp verb `which` failed     at /usr/local/lib/node_modules/element-theme/node_modules/isexe/mode.js:8:5
gyp verb `which` failed     at FSReqWrap.oncomplete (fs.js:152:21)
gyp verb `which` failed   stack: 'Error: not found: python2\n    at getNotFoundError (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:13:12)\n    at F (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:68:19)\n    at E (/usr/local/lib/node_modules/element-theme/node_modules/which/which.js:80:29)\n    at /usr/local/lib/node_modules/element-theme/node_modules/which/which.js:89:16\n    at /usr/local/lib/node_modules/element-theme/node_modules/isexe/index.js:42:5\n    at /usr/local/lib/node_modules/element-theme/node_modules/isexe/mode.js:8:5\n    at FSReqWrap.oncomplete (fs.js:152:21)',
gyp verb `which` failed   code: 'ENOENT' }
gyp verb check python checking for Python executable "python" in the PATH
gyp verb `which` succeeded python /usr/bin/python
gyp verb check python version `/usr/bin/python -c "import platform; print(platform.python_version());"` returned: "2.7.10\n"
gyp verb get node dir no --target version specified, falling back to host node version: 8.9.3
gyp verb command install [ '8.9.3' ]
gyp verb install input version string "8.9.3"
gyp verb install installing version: 8.9.3
gyp verb install --ensure was passed, so won't reinstall if already installed
gyp verb install version is already installed, need to check "installVersion"
gyp verb got "installVersion" 9
gyp verb needs "installVersion" 9
gyp verb install version is good
gyp verb get node dir target node version installed: 8.9.3
gyp verb build dir attempting to create "build" dir: /usr/local/lib/node_modules/element-theme/node_modules/node-sass/build
gyp ERR! configure error 
gyp ERR! stack Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/element-theme/node_modules/node-sass/build'
gyp ERR! System Darwin 17.4.0
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/element-theme/node_modules/node-gyp/bin/node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library="
gyp ERR! cwd /usr/local/lib/node_modules/element-theme/node_modules/node-sass
gyp ERR! node -v v8.9.3
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok 
Build failed with error code: 1
npm WARN element-theme@2.0.1 requires a peer of element-theme-chalk@* but none is installed. You must install peer dependencies yourself.

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! node-sass@4.8.3 postinstall: `node scripts/build.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the node-sass@4.8.3 postinstall script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/liangyuefang/.npm/_logs/2018-04-02T09_26_47_851Z-debug.log