Npm prepublish script webpack not found

I am trying to modify a npm module and I want to include the modified module as a local dependency.

When deploying this app on hosting, I am facing a strange webpack not found problem. I managed to reproduce the problem in my local machine by removing webpack globally.

My package.json:

1) I try to include the local module in package.json dependencies:

{
  "name": "parse-server-example",
  "version": "1.4.0",
  "description": "An example Parse API server using the parse-server module",
  "main": "index.js",
  "repository": {
    "type": "git",
    "url": "https://github.com/ParsePlatform/parse-server-example"
  },
  "license": "MIT",
  "dependencies": {
    "webpack": "2.3.3",
    "express": "~4.11.x",
    "kerberos": "~0.0.x",
    "parse": "~1.8.0",
    "parse-dashboard-simple": "./parse-dashboard-simple",
    "parse-server": "*"
  },
  "scripts": {
    "start": "node index.js"
  },
  "engines": {
    "node": "7.6.0"
  }
}

Take note that I have a local module called "./parse-dashboard-simple".

My local module's package.json:

{
  "name": "parse-dashboard",
  "parseDashboardFeatures": [
    "Data Browser",
    "Cloud Code Viewer",
    "Cloud Code Jobs Viewer and Runner",
    "Parse Config",
    "API Console",
    "Class Level Permissions Editor",
    "Pointer Permissions Editor",
    "Send Push Notifications",
    "Logs Viewer",
    "Push Status Page",
    "Relation Editor"
  ],
  "description": "The Parse Dashboard",
  "keywords": [
    "parse",
    "dashboard"
  ],
  "homepage": "https://github.com/ParsePlatform/parse-dashboard",
  "bugs": "https://github.com/ParsePlatform/parse-dashboard/issues",
  "version": "1.0.25",
  "repository": {
    "type": "git",
    "url": "https://github.com/ParsePlatform/parse-dashboard"
  },
  "license": "SEE LICENSE IN LICENSE",
  "files": [
    "Parse-Dashboard",
    "bin",
    "README.md",
    "LICENSE"
  ],
  "dependencies": {
    "bcryptjs": "^2.3.0",
    "body-parser": "^1.15.2",
    "commander": "^2.9.0",
    "connect-flash": "^0.1.1",
    "cookie-session": "^2.0.0-alpha.1",
    "csurf": "^1.9.0",
    "express": "^4.13.4",
    "json-file-plus": "^3.2.0",
    "package-json": "^2.3.1",
    "passport": "^0.3.2",
    "passport-local": "^1.0.0",
    "webpack": "~1.12.0"
  },
  "devDependencies": {
    "babel-core": "~5.8.12",
    "babel-loader": "~5.3.0",
    "babel-plugin-remove-proptypes": "~1.0.0",
    "babel-polyfill": "^6.7.2",
    "babel-runtime": "~5.8.25",
    "css-loader": "~0.18.0",
    "file-loader": "^0.8.5",
    "history": "^2.1.2",
    "http-server": "~0.8.5",
    "immutable": "~3.7.5",
    "immutable-devtools": "~0.0.4",
    "jest-cli": "^12.0.2",
    "js-beautify": "~1.5.0",
    "marked": "^0.3.5",
    "node-sass": "^3.7.0",
    "parse": "1.6.14",
    "prismjs": "~1.2.0",
    "react": "^15.0.1",
    "react-addons-test-utils": "^15.0.1",
    "react-dnd": "~2.1.4",
    "react-dnd-html5-backend": "~2.0.0",
    "react-dom": "^15.0.1",
    "react-router": "^2.6.0",
    "request-promise": "^4.1.1",
    "sass-loader": "~3.1.2",
    "style-loader": "~0.12.3",
    "svg-prep": "~1.0.0",
    "transform-jest-deps": "^2.1.0",
    "webpack": "~1.12.0"
  },
  "scripts": {
    "dev": "node ./Parse-Dashboard/index.js & webpack --config webpack/build.config.js --devtool eval-source-map --progress --watch",
    "dashboard": "node ./Parse-Dashboard/index.js & webpack --config webpack/build.config.js --progress --watch",
    "pig": "http-server ./PIG -p 4041 -s & webpack --config webpack/PIG.config.js --progress --watch",
    "build": "NODE_ENV=production webpack --config webpack/production.config.js && webpack --config webpack/PIG.config.js",
    "test": "NODE_PATH=./node_modules jest",
    "generate": "node scripts/generate.js",
    "prepublish": "webpack --config webpack/publish.config.js",
    "start": "node ./Parse-Dashboard/index.js"
  },
  "bin": {
    "parse-dashboard": "./bin/parse-dashboard"
  },
  "engines": {
    "node": "7.6.0"
  },
  "main": "Parse-Dashboard/app.js",
  "jest": {
    "testPathDirs": [
      "src/lib"
    ],
    "scriptPreprocessor": "<rootDir>/testing/preprocessor.js",
    "testDirectoryName": "tests",
    "testFileExtensions": [
      "test.js"
    ],
    "unmockedModulePathPatterns": [
      "react",
      "react-dom",
      "react-addons-test-utils",
      "fbjs"
    ]
  }
}

If I run "npm install" at the root level of this project, I will get this error:

npm WARN prepublish-on-install As of npm@5, `prepublish` scripts will run only for `npm publish`.
npm WARN prepublish-on-install (In npm@4 and previous versions, it also runs for `npm install`.)
npm WARN prepublish-on-install See the deprecation note in `npm help scripts` for more information.

> parse-dashboard@1.0.25 prepublish /Users/jhyhaurtee/Documents/Codes/Playgrounds/tplusbackend/parse-dashboard-advanced
> webpack --config webpack/publish.config.js

sh: webpack: command not found
npm ERR! addLocal Could not install /Users/jhyhaurtee/Documents/Codes/Playgrounds/tplusbackend/parse-dashboard-advanced
npm ERR! addLocal Could not install /Users/jhyhaurtee/Documents/Codes/Playgrounds/tplusbackend/parse-dashboard-simple
npm WARN Local package.json exists, but node_modules missing, did you mean to install?
npm ERR! Darwin 16.5.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install"
npm ERR! node v7.6.0
npm ERR! npm  v4.1.2
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn

npm ERR! parse-dashboard@1.0.25 prepublish: `webpack --config webpack/publish.config.js`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the parse-dashboard@1.0.25 prepublish script 'webpack --config webpack/publish.config.js'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the parse-dashboard package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     webpack --config webpack/publish.config.js
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs parse-dashboard
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls parse-dashboard
npm ERR! There is likely additional logging output above.

So my understanding is that the webpack is needed in prepublish script but it is not found. But I have intentionally added webpack as dependencies in both root project or the local module, why is it still not found?

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