当npm install 的时候，报如下错误：

Building: G:\nodejs\node.exe F:\test\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   'G:\\nodejs\\node.exe',
gyp verb cli   'F:\\test\\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@12.13.0 | 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:\test\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\test\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\test\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\test\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\test\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\test\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:158:21)
gyp verb `which` failed  python2 Error: not found: python2
gyp verb `which` failed     at getNotFoundError (F:\test\node_modules\which\which.js:13:12)
gyp verb `which` failed     at F (F:\test\node_modules\which\which.js:68:19)
gyp verb `which` failed     at E (F:\test\node_modules\which\which.js:80:29)
gyp verb `which` failed     at F:\test\node_modules\which\which.js:89:16
gyp verb `which` failed     at F:\test\node_modules\isexe\index.js:42:5
gyp verb `which` failed     at F:\test\node_modules\isexe\windows.js:36:5
gyp verb `which` failed     at FSReqCallback.oncomplete (fs.js:158:21) {
gyp verb `which` failed   stack: 'Error: not found: python2\n' +
gyp verb `which` failed     '    at getNotFoundError (F:\\test\\node_modules\\which\\which.js:13:12)\n' +
gyp verb `which` failed     '    at F (F:\\test\\node_modules\\which\\which.js:68:19)\n' +
gyp verb `which` failed     '    at E (F:\\test\\node_modules\\which\\which.js:80:29)\n' +
gyp verb `which` failed     '    at F:\\test\\node_modules\\which\\which.js:89:16\n' +
gyp verb `which` failed     '    at F:\\test\\node_modules\\isexe\\index.js:42:5\n' +
gyp verb `which` failed     '    at F:\\test\\node_modules\\isexe\\windows.js:36:5\n' +
gyp verb `which` failed     '    at FSReqCallback.oncomplete (fs.js:158:21)',
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` succeeded python G:\Python\Python37-32\python.EXE
gyp ERR! configure error
gyp ERR! stack Error: Command failed: G:\Python\Python37-32\python.EXE -c import sys; print "%s.%s.%s" % sys.version_info[:3];
gyp ERR! stack   File "<string>", line 1
gyp ERR! stack     import sys; print "%s.%s.%s" % sys.version_info[:3];
gyp ERR! stack                                ^
gyp ERR! stack SyntaxError: invalid syntax
gyp ERR! stack
gyp ERR! stack     at ChildProcess.exithandler (child_process.js:295:12)
gyp ERR! stack     at ChildProcess.emit (events.js:210:5)
gyp ERR! stack     at maybeClose (internal/child_process.js:1021:16)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:283:5)
gyp ERR! System Windows_NT 10.0.18362
gyp ERR! command "G:\\nodejs\\node.exe" "F:\\test\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsas
s_library="
gyp ERR! cwd F:\test\node_modules\node-sass
gyp ERR! node -v v12.13.0
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok
Build failed with error code: 1
npm WARN ajv-keywords@2.1.1 requires a peer of ajv@^5.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.4 (node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.4: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! node-sass@4.11.0 postinstall: `node scripts/build.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the node-sass@4.11.0 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!     C:\Users\Administrator\AppData\Roaming\npm-cache\_logs\2019-11-18T07_33_10_767Z-debug.log

Process finished with exit code 1

解决办法：

1. 运行 npm install --global windows-build-tools --save
2. 再安装node-sass npm install node-sass --save

到这里，错误应该就已经解决了。
如果 node-sass 安装不上的话可以试试用 cnpm 镜像安装。