これを試してみると、エラーがスローされます。どうすれば解決できますか?
$ hexo generate
ERROR Error: Cannot find module 'bluebird'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Object.<anonymous> (/Users/lihz/blog/node_modules/hexo/lib/hexo/index.js:3:15)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at /usr/local/lib/node_modules/hexo-cli/lib/index.js:73:18
at tryCatcher (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/util.js:26:23)
at Promise._settlePromiseFromHandler (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/promise.js:489:31)
at Promise._settlePromiseAt (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/promise.js:565:18)
at Promise._settlePromises (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/promise.js:681:14)
Unhandled rejection TypeError: Cannot call method 'then' of undefined
at /usr/local/lib/node_modules/hexo-cli/lib/index.js:82:22
at tryCatcher (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/util.js:26:23)
at Promise._settlePromiseFromHandler (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/promise.js:489:31)
at Promise._settlePromiseAt (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/promise.js:565:18)
at Async._drainQueue (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/async.js:128:12)
at Async._drainQueues (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/async.js:133:10)
at Async.drainQueues (/usr/local/lib/node_modules/hexo-cli/node_modules/bluebird/js/main/async.js:15:14)
at process._tickCallback (node.js:442:13)