# Buggy code
def refresh_sourcelist_data(self, rerun=True):
    """
    delete all the source in the list and adding a new one
    """

    # don't refresh if we are quitting
    if GUIUtility.getInstance().utility.abcquitting:
        return

    for i in xrange(0, self.GetItemCount()):
        item = self.GetItem(i)
        data = item.GetData()

        if isinstance(data, ChannelSource):
            if item.GetText() == "Loading..":
                item.SetText(data.get_source_text() or "Loading..")
                self.SetItem(item)

    if (
        rerun
        and not self.guiutility.utility.session.lm.threadpool.is_pending_task_active(
            str(self) + "_refresh_data_ULC"
        )
    ):
        self.guiutility.utility.session.lm.threadpool.add_task(
            self.refresh_sourcelist_data, 30, task_name=str(self) + "_refresh_data_ULC"
        )


# 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 refresh_sourcelist_data(self, rerun=True):
    """
    delete all the source in the list and adding a new one
    """

    # don't refresh if we are quitting
    if GUIUtility.getInstance().utility.abcquitting:
        return

    for i in xrange(0, self.GetItemCount()):
        item = self.GetItem(i)
        data = item.GetData()

        if isinstance(data, ChannelSource):
            if item.GetText() == "Loading..":
                item.SetText(data.get_source_text() or "Loading..")
                self.SetItem(item)

    if rerun and not self.is_pending_task_active(str(self) + "_refresh_data_ULC"):
        self.register_task(
            str(self) + "_refresh_data_ULC",
            reactor.callLater(30, self.refresh_sourcelist_data),
        )