ERROR: Uncaught exception in luigi
Traceback (most recent call last):

  File "/home/thanusha/.venvs/edx-analytics-pipeline/local/lib/python2.7/site-packages/luigi/retcodes.py", line 74, in run_with_retcodes
    worker = luigi.interface._run(argv)['worker']

  File "/home/thanusha/.venvs/edx-analytics-pipeline/local/lib/python2.7/site-packages/luigi/interface.py", line 248, in _run
    return _schedule_and_run([cp.get_task_obj()], worker_scheduler_factory)

  File "/home/thanusha/.venvs/edx-analytics-pipeline/local/lib/python2.7/site-packages/luigi/cmdline_parser.py", line 116, in get_task_obj
    return self._get_task_cls()(**self._get_task_kwargs())

  File "/home/thanusha/.venvs/edx-analytics-pipeline/local/lib/python2.7/site-packages/luigi/cmdline_parser.py", line 133, in _get_task_kwargs
    res.update(((param_name, param_obj.parse(attr)),))

  File "/home/thanusha/.venvs/edx-analytics-pipeline/local/lib/python2.7/site-packages/luigi/parameter.py", line 940, in parse
    return list(json.loads(x, object_pairs_hook=_FrozenOrderedDict))

  File "/usr/lib/python2.7/json/__init__.py", line 352, in loads
    return cls(encoding=encoding, **kw).decode(s)

  File "/usr/lib/python2.7/json/decoder.py", line 365, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())

  File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode
    raise ValueError("No JSON object could be decoded")

ValueError: No JSON object could be decoded