未解决：运行EtherCalc出错：Error: Cannot find module 'zappajs'

下载：

git clone --branch master https://github.com/audreyt/ethercalc.git

出错：

# bin/ethercalc
node app.js
Please connect to: http://debian:8000/
internal/modules/cjs/loader.js:583
    throw err;
    ^

Error: Cannot find module 'zappajs'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:581:15)
    at Function.Module._load (internal/modules/cjs/loader.js:507:25)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:22:18)
    at Object. (/home/quantum6/ethercalc/app.js:49:3)
    at Object. (/home/quantum6/ethercalc/app.js:60:4)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)

　　开源的东西，这是正常现象。