npm安装node-sass失败解决办法

npm安装node-sass总是报错，错误信息如下：

Building: D:\Program Files (x86)\nodejs\node.exe F:\workspace_vue\project\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 [
gyp verb cli   'D:\\Program Files (x86)\\nodejs\\node.exe',
gyp verb cli   'F:\\workspace_vue\\project\\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 verb cli ]
gyp info using node-gyp@3.8.0
gyp info using node@12.17.0 | win32 | 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 (F:\workspace_vue\project\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\workspace_vue\project\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\workspace_vue\project\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:167:21)
gyp verb `which` failed  python2 Error: not found: python2
gyp verb `which` failed     at getNotFoundError (F:\workspace_vue\project\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\workspace_vue\project\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\workspace_vue\project\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:167:21) {
gyp verb `which` failed   code: 'ENOENT'
gyp verb `which` failed }
gyp verb check python checking for Python executable "python" in the PATH
gyp verb `which` failed Error: not found: python
gyp verb `which` failed     at getNotFoundError (F:\workspace_vue\project\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\workspace_vue\project\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\workspace_vue\project\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:167:21)
gyp verb `which` failed  python Error: not found: python
gyp verb `which` failed     at getNotFoundError (F:\workspace_vue\project\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\workspace_vue\project\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\workspace_vue\project\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\workspace_vue\project\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:167:21) {
gyp verb `which` failed   code: 'ENOENT'
gyp verb `which` failed }
gyp verb could not find "python". checking python launcher
gyp verb could not find "python". guessing location
gyp verb ensuring that file exists: C:\Python27\python.exe
gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "python", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (F:\workspace_vue\project\node_modules\node-gyp\lib\configure.js:484:19)
gyp ERR! stack     at PythonFinder.<anonymous> (F:\workspace_vue\project\node_modules\node-gyp\lib\configure.js:509:16)
gyp ERR! stack     at callback (F:\workspace_vue\project\node_modules\graceful-fs\polyfills.js:295:20)
gyp ERR! stack     at FSReqCallback.oncomplete (fs.js:167:21)
gyp ERR! System Windows_NT 6.1.7601
gyp ERR! command "D:\\Program Files (x86)\\nodejs\\node.exe" "F:\\workspace_vue\\project\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library="
gyp ERR! cwd F:\workspace_vue\project\node_modules\node-sass
gyp ERR! node -v v12.17.0
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok

错误原因：
node-sass会依赖一个二进制文件binding.node，当下载node-sass时，会先下载这个文件，如果本地没有安装过这个文件，会在github下载该文件并将其缓存到全局;一般下载的时候会因为网络的原因下载失败，node-sass会尝试在本地编译binding.node，这个过程就需要用python。这时就会报错说没安装python，如果binding.node下载成功的话就不会报这个错

解决办法：将npm源设置成淘宝镜像源，将binding.node源也改为淘宝镜像源

npm config set registry https://registry.npm.taobao.org
npm config set SASS_BINARY_SITE=https://npm.taobao.org/mirrors/node-sass/

如果本地已经有了node-sass，要先把之前的卸载

npm uninstall node-sass

安装node-sass即可安装成功