use correct module imports to avoid conflicting models error while arting celery workers

[ziafazal]

Celery workers were not able to run due to conflicting models imports. This PR fixes the issue.

Here is the error trace

Traceback (most recent call last):
  File "./manage.py", line 116, in <module>
    execute_from_command_line([sys.argv[0]] + django_args)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 346, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/djcelery/management/commands/celery.py", line 23, in run_from_argv
    ['{0[0]} {0[1]}'.format(argv)] + argv[2:],
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/celery.py", line 769, in execute_from_commandline
    super(CeleryCommand, self).execute_from_commandline(argv)))
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/base.py", line 311, in execute_from_commandline
    return self.handle_argv(self.prog_name, argv[1:])
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/celery.py", line 761, in handle_argv
    return self.execute(command, argv)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/celery.py", line 693, in execute
    ).run_from_argv(self.prog_name, argv[1:], command=argv[0])
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/worker.py", line 179, in run_from_argv
    return self(*args, **options)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/base.py", line 274, in __call__
    ret = self.run(*args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/bin/worker.py", line 212, in run
    state_db=self.node_format(state_db, hostname), **kwargs
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/worker/__init__.py", line 95, in __init__
    self.app.loader.init_worker()
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/loaders/base.py", line 128, in init_worker
    self.import_default_modules()
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/loaders/base.py", line 116, in import_default_modules
    signals.import_modules.send(sender=self.app)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/utils/dispatch/signal.py", line 166, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/amqp/utils.py", line 42, in __call__
    self.set_error_state(exc)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/amqp/utils.py", line 39, in __call__
    **dict(self.kwargs, **kwargs) if self.kwargs else kwargs
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/app/base.py", line 329, in _autodiscover_tasks
    self.loader.autodiscover_tasks(packages, related_name)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/loaders/base.py", line 251, in autodiscover_tasks
    related_name) if mod)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/loaders/base.py", line 272, in autodiscover_tasks
    return [find_related_module(pkg, related_name) for pkg in packages]
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/celery/loaders/base.py", line 298, in find_related_module
    return importlib.import_module('{0}.{1}'.format(package, related_name))
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/edx/app/edxapp/venvs/edxapp/src/problem-builder/problem_builder/tasks.py", line 8, in <module>
    from lms.djangoapps.instructor_task.models import ReportStore
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor_task/models.py", line 35, in <module>
    class InstructorTask(models.Model):
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/db/models/base.py", line 309, in __new__
    new_class._meta.apps.register_model(new_class._meta.app_label, new_class)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/apps/registry.py", line 221, in register_model
    (model_name, app_label, app_models[model_name], model))
RuntimeError: Conflicting 'instructortask' models in application 'instructor_task': <class 'instructor_task.models.InstructorTask'> and <class 'lms.djangoapps.instructor_task.models.InstructorTask'>.

@pomegranited would you please review and merge?
@bradenmacdonald FYI.

[pomegranited]

Hi @ziafazal , we had to change the paths to use lms.djangoapps.instructor_task.models to match what was used in edx-platform. So I think the solution is to fix the paths in edx-platform to make them match upstream?

cf #128, edx/edx-platform@54d34e8

CC @bradenmacdonald

[bradenmacdonald]

Different paths are needed in Eucalyptus vs. post-Eucalyptus. This master branch uses the post-Eucalyptus version, and I don't want to change that. We could create a "legacy" branch that includes that commit, and use it on the solutions fork until they upgrade to Ficus.

[pomegranited]

@ziafazal Does @bradenmacdonald 's suggestion work for you?

[ziafazal]

@pomegranited we can close this PR since we cherry picked 54d34e8 into Eucalyptus upgrade of solutions fork.

[pomegranited]

Thanks, @ziafazal !