Polymer: gulp error at build time: merge-stream
问题 I'm trying to run gulp to build my app like Rob Dodson explains here, but I get the following error: module.js:327 throw err; ^ Error: Cannot find module 'merge-stream' at Function.Module._resolveFilename (module.js:325:15) at Function.Module._load (module.js:276:25) at Module.require (module.js:353:17) at require (internal/module.js:12:17) at Object.<anonymous> (/Users/path/to/gulpfile.js:16:21) at Module._compile (module.js:409:26) at Object.Module._extensions..js (module.js:416:10) at