Issue 6822 - Report browser test errors

test_runner.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 143 matching lines @@
                                   file).replace(/\.js$/, "")
           )
         )
         // We need to convert rejected promise to a resolved one
         // or the test will not let close the webdriver.
         .catch(e => e)
     )).then(results =>
     {
       let errors = results.filter(e => typeof e != "undefined");
       if (errors.length)
-        return Promise.reject(`Unit test failed: ${errors.join(", ")}`);
+        throw `Browser unit test failed: ${errors.join(", ")}`;
     })
   );
 }
 
 if (process.argv.length > 2)
   addTestPaths(process.argv.slice(2), true);
 else
 {
   addTestPaths(
     [path.join(__dirname, "test"), path.join(__dirname, "test", "browser")],
     true
   );
 }
 
 runBrowserTests(runnerProcesses).then(() =>
 {
   if (unitFiles.length)
     nodeunit.reporters.default.run(unitFiles);
 }).catch(error =>
 {
-  if (!error)
-    console.error("Failed running browser tests");
-  else
-    console.error(error);
+  console.error(error);
   process.exit(1);
 });