Issue 6822 - Report browser test errors

test/runners/firefox_process.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present 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 28 matching lines @@
   const driver = new Builder()
         .forBrowser("firefox")
         .setFirefoxOptions(options)
         .build();
 
   return executeScript(driver, "Firefox", script, scriptName, scriptArgs);
 }
 
 module.exports = function(script, scriptName, ...scriptArgs)
 {
-  return ensureFirefox(FIREFOX_VERSION).then(firefoxPath =>
-  {
-    return runScript(firefoxPath, script, scriptName, scriptArgs)
-      .then(result => result)
-      .catch(error =>
-      {
-        throw error;
-      });
-  });
+  return ensureFirefox(FIREFOX_VERSION)
+    .then(firefoxPath =>
+          runScript(firefoxPath, script, scriptName, scriptArgs));
 };