# Buggy code
def waitForHandleAndSynchronize(default=None):
    def wrap(f):
        def invoke_func(*args, **kwargs):
            download = args[0]
            with download.dllock:
                if download.handle and download.handle.is_valid():
                    return f(*args, **kwargs)
                else:
                    lambda_f = lambda a=args, kwa=kwargs: invoke_func(*a, **kwa)
                    download.session.lm.threadpool.add_task(lambda_f, 1)
                    return default

        return invoke_func

    return wrap


# Traceback (isError)
Regression

Tribler.Test.Core.Modules.RestApi.test_downloads_endpoint.TestDownloadsEndpoint.test_remove_download_no_remove_data_param (from nosetests)
Failing for the past 1 build (Since Failed#2109 )
Took 4.4 sec.
Error Message

Test raised 1 unhandled Twisted exceptions:
[{'log_namespace': u'log_legacy', 'log_time': 1467938979.639, 'format': '%(log_legacy)s', 'log_system': '-', 'log_legacy': <twisted.logger._stdlib.StringifiableFromEvent object at 0x06D22830>, 'log_level': <LogLevel=critical>, 'system': '-', 'isError': 1, 'failure': <twisted.python.failure.Failure exceptions.AttributeError: 'NoneType' object has no attribute 'add_task'>, 'time': 1467938979.639, 'log_text': 'Unhandled Error\nTraceback (most recent call last):\n  File "C:\\Python27\\lib\\threading.py", line 763, in run\n    self.__target(*self.__args, **self.__kwargs)\n  File "C:\\workspace\\jenkins\\workspace\\GH_Tribler_PR_tests_win32\\tribler\\Tribler\\Core\\Utilities\\twisted_thread.py", line 55, in _reactor_runner\n    reactor.run(installSignalHandlers=False)\n  File "C:\\Python27\\lib\\site-packages\\twisted\\internet\\base.py", line 1194, in run\n    self.mainLoop()\n  File "C:\\Python27\\lib\\site-packages\\twisted\\internet\\base.py", line 1203, in mainLoop\n    self.runUntilCurrent()\n--- <exception caught here> ---\n  File "C:\\Python27\\lib\\site-packages\\twisted\\internet\\base.py", line 825, in runUntilCurrent\n    call.func(*call.args, **call.kw)\n  File "C:\\workspace\\jenkins\\workspace\\GH_Tribler_PR_tests_win32\\tribler\\Tribler\\Core\\Libtorrent\\__init__.py", line 27, in <lambda>\n    lambda_f = lambda a = args, kwa = kwargs: invoke_func(*a, **kwa)\n  File "C:\\workspace\\jenkins\\workspace\\GH_Tribler_PR_tests_win32\\tribler\\Tribler\\Core\\Libtorrent\\__init__.py", line 28, in invoke_func\n    download.session.lm.threadpool.add_task(lambda_f, 1)\nexceptions.AttributeError: \'NoneType\' object has no attribute \'add_task\'\n', 'log_format': u'{log_text}', 'message': (), 'why': None}]

# Fixed code
def waitForHandleAndSynchronize(default=None):
    def wrap(f):
        def invoke_func(*args, **kwargs):
            download = args[0]
            with download.dllock:
                if download.handle and download.handle.is_valid():
                    return f(*args, **kwargs)
                elif not download.session.lm.shutdownstarttime:
                    lambda_f = lambda a=args, kwa=kwargs: invoke_func(*a, **kwa)
                    random_id = "".join(
                        random.choice("0123456789abcdef") for _ in xrange(30)
                    )
                    reactor.callFromThread(
                        lambda: download.register_task(
                            "check_handle_%s" % random_id,
                            reactor.callLater(1, lambda_f),
                        )
                    )
                return default

        return invoke_func

    return wrap