Update to eslint 6

This updates eslint and related plugins to the next major version so
that we can make use of new features.

.eslintrc.yml

@@ -51,8 +51,10 @@ rules:
   no-jquery/no-serialize: error
   promise/always-return: off
   promise/no-callback-in-promise: off
+  # Make update to eslint@6 smoother:
+  prefer-object-spread: off
 overrides:
-  files:
+  - files:
       - '**/spec/**/*'
     rules:
       "@gitlab/i18n/no-non-i18n-strings": off

package.json

@@ -146,9 +146,9 @@
   },
   "devDependencies": {
     "@babel/plugin-transform-modules-commonjs": "^7.5.0",
-    "@gitlab/eslint-config": "^2.1.2",
+    "@gitlab/eslint-config": "^3.0.0",
     "@gitlab/eslint-plugin-i18n": "^1.1.0",
-    "@gitlab/eslint-plugin-vue-i18n": "^1.2.0",
+    "@gitlab/eslint-plugin-vue-i18n": "^2.0.0",
     "@vue/test-utils": "^1.0.0-beta.30",
     "axios-mock-adapter": "^1.15.0",
     "babel-jest": "^24.1.0",
@@ -159,10 +159,10 @@
     "commander": "^2.18.0",
     "custom-jquery-matchers": "^2.1.0",
     "docdash": "^1.0.2",
-    "eslint": "~5.9.0",
-    "eslint-import-resolver-jest": "^2.1.1",
-    "eslint-import-resolver-webpack": "^0.10.1",
-    "eslint-plugin-jasmine": "^2.10.1",
+    "eslint": "~6.8.0",
+    "eslint-import-resolver-jest": "^3.0.0",
+    "eslint-import-resolver-webpack": "^0.12.1",
+    "eslint-plugin-jasmine": "^4.1.0",
     "eslint-plugin-jest": "^22.3.0",
     "eslint-plugin-no-jquery": "^2.3.0",
     "gettext-extractor": "^3.4.3",

spec/frontend/.eslintrc.yml

@@ -6,6 +6,12 @@ plugins:
 extends:
   - 'plugin:jest/recommended'
 settings:
+  # We have to teach eslint-plugin-import what node modules we use
+  # otherwise there is an error when it tries to resolve them
+  import/core-modules:
+    - events
+    - fs
+    - path  
   import/resolver:
     jest:
       jestConfigFile: 'jest.config.js'