title: JHipster is producing error while building for production
body: <p>I'm using JHipster 5.3.4. The production build producing the following error. I have cleared all the packages and re-installed them. Its still producing the error. 'dev' build works fine. It's only appearing after the upgrade to new version of JHipster, v5.3.4. I do not know what's causing the problem.</p>
  
  <p>It starts by producing this error : '[ERROR] (node:9240) DeprecationWarning: Tapable.plugin is deprecated. Use 
      new API on <code>.hooks</code> instead'.</p>
  
  <pre><code>[INFO] &gt; node --max_old_space_size=4096 node_modules/webpack/bin/webpack.js 
  "--config" "webpack/webpack.prod.js" "--profile"
  [ERROR] (node:9240) DeprecationWarning: Tapable.plugin is deprecated. Use 
  new API on `.hooks` instead
  [ERROR] Error: Parse error on line 1:
  [ERROR] (* 1.25) + 4px
  [ERROR] Expecting 'SUB', 'LPAREN', 'NESTED_CALC', 'NUMBER', 'CSS_VAR', 
  'LENGTH', 'ANGLE', 'TIME', 'FREQ', 'RES', 'EMS', 'EXS', 'CHS', 'REMS', 
  'VHS', 'VWS', 'VMINS', 'VMAXS', 'PERCENTAGE', got 'MUL'
  [ERROR]     at Parser.parseError (D:\Projects\arif\fb- 
  quiz\node_modules\cssnano-preset-default\node_modules\reduce-css- 
  calc\dist\parser.js:160:21)
  [ERROR]     at Parser.parse (D:\Projects\arif\fb-quiz\node_modules\cssnano- 
  preset-default\node_modules\reduce-css-calc\dist\parser.js:226:22)
  [ERROR]     at D:\Projects\arif\fb-quiz\node_modules\cssnano-preset- 
  default\node_modules\reduce-css-calc\dist\index.js:35:30
  [ERROR]     at walk (D:\Projects\arif\fb-quiz\node_modules\postcss-value- 
  parser\lib\walk.js:15:13)
  [ERROR]     at ValueParser.walk (D:\Projects\arif\fb- 
  quiz\node_modules\postcss-value-parser\lib\index.js:18:5)
  [ERROR]     at exports.default (D:\Projects\arif\fb- 
  quiz\node_modules\cssnano-preset-default\node_modules\reduce-css- 
  calc\dist\index.js:29:51)
  [ERROR]     at transformValue (D:\Projects\arif\fb- 
  quiz\node_modules\cssnano-preset-default\node_modules\postcss- 
  calc\dist\lib\transform.js:24:45)
  [ERROR]     at exports.default (D:\Projects\arif\fb- 
  quiz\node_modules\cssnano-preset-default\node_modules\postcss-
  calc\dist\lib\transform.js:54:100)
  [ERROR]     at D:\Projects\arif\fb-quiz\node_modules\cssnano-preset-default\node_modules\postcss-calc\dist\index.js:28:52
  [ERROR]     at D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:144:26
  [ERROR]     at Rule.each (D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:110:22)
  [ERROR]     at Rule.walk (D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:143:21)
  [ERROR]     at D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:146:32
  [ERROR]     at Root.each (D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:110:22)
  [ERROR]     at Root.walk (D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\postcss\lib\container.js:143:21)
  [ERROR]     at D:\Projects\arif\fb-quiz\node_modules\cssnano-preset-default\node_modules\postcss-calc\dist\index.js:25:9
  [ERROR]     at initializePlugin (D:\Projects\arif\fb-quiz\node_modules\optimize-css-assets-webpack-plugin\node_modules\cssnano\dist\index.js:35:51)
  [ERROR]     at &lt;anonymous&gt;
  [ERROR] npm ERR! code ELIFECYCLE
  [ERROR] npm ERR! errno 1
  [ERROR] npm ERR! fb-quiz@0.0.0 webpack: `node --max_old_space_size=4096 node_modules/webpack/bin/webpack.js "--config" "webpack/webpack.prod.js" "--profile"
  [ERROR] npm ERR! Failed at the fb-quiz@0.0.0 webpack script.
  [ERROR] npm ERR! code ELIFECYCLE
  [ERROR] npm ERR! errno 1
  [ERROR] npm ERR! fb-quiz@0.0.0 webpack:prod:main: `npm run webpack -- --config webpack/webpack.prod.js --profile`
  [ERROR] npm ERR! Failed at the fb-quiz@0.0.0 webpack:prod:main script.
  [ERROR] npm ERR! code ELIFECYCLE
  [ERROR] npm ERR! errno 1
  [ERROR] npm ERR! fb-quiz@0.0.0 webpack:prod: `npm run cleanup &amp;&amp; npm run webpack:prod:main &amp;&amp; npm run clean-www`
  [ERROR] npm ERR! Failed at the fb-quiz@0.0.0 webpack:prod script.
  [INFO] BUILD FAILURE
  [ERROR] Failed to execute goal com.github.eirslett:frontend-maven-plugin:1.6:npm (webpack build prod) on project fb-quiz: Failed to run task: 'npm run webpack:prod' failed. org.apache.commons.exec.ExecuteException: Process exited with an error: 1
  </code></pre>