Issue 3692 - Enable the no-unused-vars ESLint rule

eslint-config-eyeo/index.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 51 matching lines @@
     "no-lone-blocks": "error",
     "no-lonely-if": "error",
     "no-multi-spaces": "error",
     "no-new-func": "error",
     "no-new-object": "error",
     "no-proto": "error",
     "no-self-compare": "error",
     "no-shadow": "error",
     "no-trailing-spaces": "error",
     "no-unneeded-ternary": "error",
-    "no-unused-vars": "off",
+    "no-unused-vars": ["error", {vars: "local", args: "none"}],
     "no-useless-computed-key": "error",
     "no-useless-concat": "error",
     "no-useless-escape": "error",
     "no-useless-return": "error",
     "no-var": "error",
     "no-warning-comments": "error",
     "no-whitespace-before-property": "error",
     "no-with": "error",
     "object-curly-spacing": "error",
     "object-shorthand": ["error", "always", {
@@ skipping 22 matching lines @@
     "strict": ["error", "global"],
     "valid-jsdoc": ["error", {
       requireParamDescription: false,
       requireReturn: false,
       requireReturnDescription: false
     }],
     "yield-star-spacing": "error",
     "yoda": "error"
   }
 };