[2694] v1.2.0 Cannot find module 'postcss-import-resolver'

I updated it soon. from v1.1.1, yarn && yarn dev

Error: Cannot find module 'postcss-import-resolver'
    at Function.Module._resolveFilename (module.js:555:15)
    at Function.Module._load (module.js:482:25)
    at Module.require (module.js:604:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (...myproj/node_modules/nuxt/lib/builder/webpack/postcss.js:5:24)
    at Module._compile (module.js:660:30)
    at Object.Module._extensions..js (module.js:671:10)
    at Module.load (module.js:573:32)
    at tryModuleLoad (module.js:513:12)
    at Function.Module._load (module.js:505:3)
    at Module.require (module.js:604:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (...myproj/node_modules/nuxt/lib/builder/webpack/vue-loader.js:1:85)
    at Module._compile (module.js:660:30)
    at Object.Module._extensions..js (module.js:671:10)
    at Module.load (module.js:573:32)
error Command failed with exit code 1.

Running yarn upgrade was a similar result. For now, I solved it by running yarn add postcss-import-resolver.

and... running log,

  nuxt:render Rendering url /admin/users/assets/styles/main.css.map +846ms
{ statusCode: 404,
  path: '/admin/users/assets/styles/main.css.map',
  message: 'This page could not be found' }
  nuxt:render Rendering url /admin/users/assets/styles/app.css.map +43ms
{ statusCode: 404,
  path: '/admin/users/assets/styles/app.css.map',
  message: 'This page could not be found' }

My Stylus files main.styl and app.styl, .map file originally has not output, but Nuxt is trying to access it automatically.

Are you performing successfully😶?