Ok so I went ahead and uninstalled uncss and I also noticed I had postuncss on it which I THINK based on the github version you showed me are the dependencies that come by default. So I ran the yarn remove <package> command to remove both packages, made sure they weren’t there but for some reason it looks like still trying to load those dependencies even though I uninstalled them.
Here is how my packages.json looks like
"devDependencies": {
"autoprefixer": "~8.2.0",
"browser-sync": "~2.24.7",
"browsersync-webpack-plugin": "^0.6.0",
"bs-html-injector": "~3.0",
"buble-loader": "^0.4.1",
"cache-loader": "~1.2.5",
"clean-webpack-plugin": "^0.1.18",
"copy-globs-webpack-plugin": "^0.2.0",
"css-loader": "^0.28.9",
"cssnano": "~4.0.5",
"eslint": "~4.19.1",
"eslint-loader": "~1.9",
"eslint-plugin-import": "~2.14.0",
"extract-text-webpack-plugin": "~3.0.2",
"file-loader": "^1.1.6",
"friendly-errors-webpack-plugin": "^1.6.1",
"glob-all": "^3.1.0",
"imagemin-mozjpeg": "~7.0.0",
"imagemin-webpack-plugin": "~2.2.0",
"import-glob": "~1.5",
"node-sass": "~4.9.4",
"postcss-loader": "~2.1.0",
"postcss-safe-parser": "~3.0",
"purgecss-webpack-plugin": "^1.6.0",
"resolve-url-loader": "~2.3.1",
"rimraf": "~2.6",
"sass-loader": "~6.0",
"style-loader": "^0.22.1",
"stylelint": "^8.4.0",
"stylelint-config-standard": "~18.2.0",
"stylelint-webpack-plugin": "^0.10.5",
"uglifyjs-webpack-plugin": "^1.3.0",
"url-loader": "^0.6.2",
"webpack": "~3.10.0",
"webpack-assets-manifest": "^1.0.0",
"webpack-cli": "^3.3.10",
"webpack-dev-middleware": "~2.0.4",
"webpack-hot-middleware": "~2.22.3",
"webpack-merge": "~4.1.4",
"yargs": "~11.0.0"
},