message: Don't use `*` versions
diff: "webextension-polyfill": "^0.2.1"
  },
  "devDependencies": {
  - "ava": "*",
  + "ava": "^0.25.0",
  "babel-core": "^6.26.0",
  "babel-loader": "^7.1.2",
  "babel-plugin-transform-es2015-modules-commonjs": "^6.26.0",
  "webext": "^1.9.1-with-submit.1",
  "webpack": "^4.0.0",
  "webpack-cli": "^2.0.6",
  - "xo": "*"
  + "xo": "^0.21.0"
  },
  "xo": {
  "envs": [
  