React starting problame

saroj@GS-GG-LP-182 ~/Documents/saroj $ npm start > mdbreact@4.8.2 start /home/saroj/Documents/saroj > yarn run sass-compile && yarn run webpack yarn run v1.12.3 $ node-sass dist/scss -o dist/css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/free/modules/animations-extended/animations-extended.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/mdb.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/accordion-extended/accordion-extended.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/cards-extended/cards-extended.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/charts/charts.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/lightbox/lightbox.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/megamenu/megamenu.css Rendering Complete, saving .css file... Wrote CSS to /home/saroj/Documents/saroj/dist/css/pro/modules/parallax/parallax.css Wrote 8 CSS files to /home/saroj/Documents/saroj/dist/css Done in 0.99s. yarn run v1.12.3 $ concurrently "webpack-dev-server --config ./webpack.dev.config.js --watch" "yarn run test" /bin/sh: 1: concurrently: not found error Command failed with exit code 127. info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command. npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! mdbreact@4.8.2 start: `yarn run sass-compile && yarn run webpack` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the mdbreact@4.8.2 start script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above. npm ERR! A complete log of this run can be found in: npm ERR! /home/saroj/.npm/_logs/2018-11-08T08_02_01_960Z-debug.log

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