Errors with new versions of `postcss`

[craigbeck]

With my web pack build I get output

Unknown error from PostCSS plugin. Your current PostCSS version is 7.0.17, but parser uses 5.2.18. Perhaps this is the source of the error below

postcss-modules-parser has a dependency on older version of postcss

$ npm ls postcss
/Users/craigbeck/dev/premise-frontend-v3
├─┬ autoprefixer@9.6.1
│ └── postcss@7.0.17 
├─┬ babel-plugin-react-css-modules@5.2.6
│ ├── postcss@7.0.17  deduped
│ ├─┬ postcss-modules@1.4.1
│ │ ├─┬ css-modules-loader-core@1.1.0
│ │ │ ├── postcss@6.0.1 
│ │ │ ├─┬ postcss-modules-extract-imports@1.1.0
│ │ │ │ └── postcss@6.0.1  deduped
│ │ │ └─┬ postcss-modules-values@1.3.0
│ │ │   └── postcss@6.0.1  deduped
│ │ └── postcss@7.0.17  deduped
│ ├─┬ postcss-modules-extract-imports@1.2.1
│ │ └── postcss@6.0.23 
│ ├─┬ postcss-modules-local-by-default@1.2.0
│ │ └── postcss@6.0.23 
│ ├─┬ postcss-modules-parser@1.1.1
│ │ └── postcss@5.2.18 
│ ├─┬ postcss-modules-scope@1.1.0
│ │ └── postcss@6.0.23 
│ └─┬ postcss-modules-values@1.3.0
│   └── postcss@6.0.23 
├─┬ css-loader@1.0.1
│ ├─┬ icss-utils@2.1.0
│ │ └── postcss@6.0.23 
│ ├── postcss@6.0.23 
│ └─┬ postcss-modules-values@1.3.0
│   └── postcss@6.0.23  deduped
├─┬ postcss-color-function@4.1.0
│ └── postcss@6.0.23 
├─┬ postcss-import@12.0.1
│ └── postcss@7.0.17  deduped
├─┬ postcss-loader@3.0.0
│ └── postcss@7.0.17  deduped
├─┬ postcss-modules-values@3.0.0
│ ├─┬ icss-utils@4.1.1
│ │ └── postcss@7.0.17  deduped
│ └── postcss@7.0.17  deduped
├─┬ postcss-nested@4.1.1
│ └── postcss@7.0.17  deduped
├─┬ stylelint@10.1.0
│ ├── postcss@7.0.17  deduped
│ ├─┬ postcss-less@3.1.4
│ │ └── postcss@7.0.17  deduped
│ ├─┬ postcss-reporter@6.0.1
│ │ └── postcss@7.0.17  deduped
│ ├─┬ postcss-safe-parser@4.0.1
│ │ └── postcss@7.0.17  deduped
│ ├─┬ postcss-sass@0.3.5
│ │ └── postcss@7.0.17  deduped
│ ├─┬ postcss-scss@2.0.0
│ │ └── postcss@7.0.17  deduped
│ └─┬ sugarss@2.0.0
│   └── postcss@7.0.17  deduped
└─┬ stylelint-order@3.0.1
  ├── postcss@7.0.17  deduped
  └─┬ postcss-sorting@5.0.1
    └── postcss@7.0.17  deduped

Looking at the code it appears it's only dependency is on postcss.plugin so thinking this may be better handled with a sibling dependency?

postcss-icss/src/index.js

Line 48 in 80fad33

module.exports = postcss.plugin("postcss-icss", (options = {}) => (