Loading PostCSS Plugin failed: Cannot find module 'postcss-import'

[ufoscout]

Importing vue-design-system on a new project created with vue-cli fails with this error:

Building for production...Starting type checking and linting service...
Using 1 worker with 2048MB memory limit
⠸  Building for production...

 ERROR  Failed to compile with 1 errors                                                                                                        3:48:37 PM

 error  in /home/ufo/workspaces/wp/wp-design-system/dist/system/system.css

Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from ./node_modules/postcss-loader/src/index.js):
Error: Loading PostCSS Plugin failed: Cannot find module 'postcss-import'

(@/home/ufo/workspaces/wp/wp-design-system/.postcssrc.js)
    at load (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/postcss-load-config/src/plugins.js:21:13)
    at Object.keys.filter.map (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/postcss-load-config/src/plugins.js:53:16)
    at Array.map (<anonymous>)
    at plugins (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/postcss-load-config/src/plugins.js:52:8)
    at config.load.then (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/postcss-load-config/src/index.js:72:18)
    at runLoaders (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/webpack/lib/NormalModule.js:301:20)
    at /home/ufo/workspaces/wp/src/ui/frontend/node_modules/loader-runner/lib/LoaderRunner.js:367:11
    at /home/ufo/workspaces/wp/src/ui/frontend/node_modules/loader-runner/lib/LoaderRunner.js:233:18
    at context.callback (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/loader-runner/lib/LoaderRunner.js:111:13)
    at Promise.resolve.then.then.catch (/home/ufo/workspaces/wp/src/ui/frontend/node_modules/postcss-loader/src/index.js:208:9)

 @ ./src/main.ts 6:0-49
 @ multi ./src/main.ts

We have the very same issue in three different machines (two ubuntu 18.04 64bit, one MacOS).

What we did:

• cloned locally this repository (we tried master and 3.5.7 branch)
• changed the package name in package.json file from 'vue-design-system' to 'wp-design-system'
• executed: npm install && npm run build:system
• in another folder, we generated a new vuejs project with vue-cli
• in the package.json of the new project we added as dependency: "wp-design-system": "file:./../../wp-design-system"
• npm install in the new project -> it works
• added to the main file in the vuejs project:

  import DesignSystem from 'wp-design-system';
  import 'wp-design-system/dist/system/system.css';
  Vue.use(DesignSystem);

• execute in the vuejs project: npm run build -> this fails and complains about postcss-import