Travis-ci出现“module.js:549 throw err; ^ Error: Cannot find module './lib/source-map-generator'”

[shaobeichen]

场景还原：本来只是为了修改几个小问题，本地也没有任何问题，但是push之后，travis-ci走构建的时候出现了错误，一度导致我有点小懵逼。

错误提示：

> node build/build.js
module.js:549
    throw err;
    ^
Error: Cannot find module './lib/source-map-generator'
    at Function.Module._resolveFilename (module.js:547:15)
    at Function.Module._load (module.js:474:25)
    at Module.require (module.js:596:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/travis/build/[secure]/blog/node_modules/postcss-reduce-transforms/node_modules/source-map/source-map.js:6:30)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Module.require (module.js:596:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/travis/build/[secure]/blog/node_modules/postcss-reduce-transforms/node_modules/postcss/lib/previous-map.js:9:18)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] build: `node build/build.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the [email protected] build 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!     /home/travis/.npm/_logs/2018-06-19T09_42_10_772Z-debug.log

这其实是node_modules包里的问题，我在网上一番搜索，试着将本地的node_modules删除重新npm i，push之后发现还是这样的错，然后想着本地没有问题，那是不是ci的问题呢，这样就想到了travis-ci.yml里面的东西，只要将缓存node_modules的代码去除即可。

cache:
  directories:
    - node_modules

这样就不会缓存node_modules了，从而问题解决。