importchannel command is broken

[christianmemije]

Summary

• importchannel command is broken

System information

• Version: 0.6
• Operating system: Linux

kolibri manage importchannel -- network bcd99d8aeef04ce6b9e25a88d87eedb7
INFO     Downloading data for channel id bcd99d8aeef04ce6b9e25a88d87eedb7
  0%|                                             | 0/239616 [00:00<?, ?it/s]
Traceback (most recent call last):
  File "/home/christian/.virtualenvs/kolibri/bin/kolibri", line 9, in <module>
    load_entry_point('kolibri', 'console_scripts', 'kolibri')()
  File "/home/christian/repos/kolibri/kolibri/utils/cli.py", line 580, in main
    manage(command, args=django_args)
  File "/home/christian/repos/kolibri/kolibri/utils/cli.py", line 411, in manage
    execute_from_command_line(argv=argv)
  File "/home/christian/.virtualenvs/kolibri/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/home/christian/.virtualenvs/kolibri/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/christian/.virtualenvs/kolibri/local/lib/python2.7/site-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/christian/.virtualenvs/kolibri/local/lib/python2.7/site-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/home/christian/repos/kolibri/kolibri/tasks/management/commands/base.py", line 98, in handle
    return self.handle_async(*args, **options)
  File "/home/christian/repos/kolibri/kolibri/content/management/commands/importchannel.py", line 89, in handle_async
    self.download_channel(options["channel_id"])
  File "/home/christian/repos/kolibri/kolibri/content/management/commands/importchannel.py", line 42, in download_channel
    self._transfer(DOWNLOAD_METHOD, channel_id)
  File "/home/christian/repos/kolibri/kolibri/content/management/commands/importchannel.py", line 73, in _transfer
    if self.is_cancelled():
  File "/home/christian/repos/kolibri/kolibri/tasks/management/commands/base.py", line 108, in is_cancelled
    self.check_for_cancel(last_stage)
TypeError: 'NoneType' object is not callable

How to reproduce

1. Use the importchannel command

Real-life consequences

• Breaks my workflow.

[rtibbles]

This is a result of the cancellable tasks changes on 0.5.x, so I am targeting the fix there.

[christianmemije]

Fixed in #2093