Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_parallel_executor/executor/parallel.py", line 67, in execute
    loop.run_until_complete(future)
  File "/usr/lib/python3.8/asyncio/base_events.py", line 603, in run_until_complete
    self.run_forever()
  File "/usr/lib/python3.8/asyncio/base_events.py", line 570, in run_forever
    self._run_once()
  File "/usr/lib/python3.8/asyncio/base_events.py", line 1823, in _run_once
    event_list = self._selector.select(timeout)
  File "/usr/lib/python3.8/selectors.py", line 468, in select
    fd_event_list = self._selector.poll(timeout, max_ev)
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_core/executor/__init__.py", line 91, in __call__
    rc = await self.task(*args, **kwargs)
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_core/task/__init__.py", line 93, in __call__
    return await task_method(*args, **kwargs)
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_ros/task/ament_cmake/build.py", line 59, in build
    rc = await extension.build(
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_cmake/task/cmake/build.py", line 87, in build
    rc = await self._reconfigure(args, env)
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_cmake/task/cmake/build.py", line 182, in _reconfigure
    buildfile = get_buildfile(cmake_cache)
  File "/home/ubuntu/.local/lib/python3.8/site-packages/colcon_cmake/task/cmake/__init__.py", line 112, in get_buildfile
    if 'Ninja' in generator:
TypeError: argument of type 'NoneType' is not iterable