superset: Building from source: npm run dev-server Error

npm run dev-server

superset@0.999.0-dev dev-server /usr/local/incubator-superset/superset/assets webpack-dev-server --mode=development --progress

sh: 1: webpack-dev-server: not found

npm ERR! Linux 4.15.0-20-generic
npm ERR! argv "/usr/bin/node" "/usr/bin/npm" "run" "dev-server"
npm ERR! node v8.10.0
npm ERR! npm  v3.5.2
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! superset@0.999.0-dev dev-server: `webpack-dev-server --mode=development --progress`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the superset@0.999.0-dev dev-server script 'webpack-dev-server --mode=development --progress'.
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 superset package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     webpack-dev-server --mode=development --progress
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs superset
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls superset
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /usr/local/incubator-superset/superset/assets/npm-debug.log