# Buggy code
def guiservthread_free_space_check(self):
    if not (self and self.frame and self.frame.SRstatusbar):
        return

    free_space = get_free_space(
        DefaultDownloadStartupConfig.getInstance().get_dest_dir()
    )
    self.frame.SRstatusbar.RefreshFreeSpace(free_space)

    storage_locations = defaultdict(list)
    for download in self.utility.session.get_downloads():
        if download.get_status() == DLSTATUS_DOWNLOADING:
            storage_locations[download.get_dest_dir()].append(download)

    show_message = False
    low_on_space = [
        path
        for path in storage_locations.keys()
        if 0 < get_free_space(path) < self.utility.read_config("free_space_threshold")
    ]
    for path in low_on_space:
        for download in storage_locations[path]:
            download.stop()
            show_message = True

    if show_message:
        wx.CallAfter(
            wx.MessageBox,
            "Tribler has detected low disk space. Related downloads have been stopped.",
            "Error",
        )

    self.utility.session.lm.threadpool.call_in_thread(
        FREE_SPACE_CHECK_INTERVAL, self.guiservthread_free_space_check
    )


# 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 guiservthread_free_space_check(self):
    free_space = get_free_space(
        DefaultDownloadStartupConfig.getInstance().get_dest_dir()
    )
    self.frame.SRstatusbar.RefreshFreeSpace(free_space)

    storage_locations = defaultdict(list)
    for download in self.utility.session.get_downloads():
        if download.get_status() == DLSTATUS_DOWNLOADING:
            storage_locations[download.get_dest_dir()].append(download)

    show_message = False
    low_on_space = [
        path
        for path in storage_locations.keys()
        if 0 < get_free_space(path) < self.utility.read_config("free_space_threshold")
    ]
    for path in low_on_space:
        for download in storage_locations[path]:
            download.stop()
            show_message = True

    if show_message:
        wx.CallAfter(
            wx.MessageBox,
            "Tribler has detected low disk space. Related downloads have been stopped.",
            "Error",
        )