[Important] Bench version 2 - see this before you run bench update

@anand after some tinkering around i get the following error in worker.error.log

"worker.error.log" [readonly] 270 lines --0%--                                                                                                                                                  1,1           Top
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 936, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 782, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 782, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 416, in invoke
    return callback(*args, **kwargs)
  File "/home/test/frappe-bench/apps/frappe/frappe/commands.py", line 1040, in start_worker
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 416, in invoke
    return callback(*args, **kwargs)
  File "/home/test/frappe-bench/apps/frappe/frappe/commands.py", line 1040, in start_worker
    start_worker(queue)
  File "/home/test/frappe-bench/apps/frappe/frappe/utils/background_jobs.py", line 72, in start_worker
    Worker(queues, name=get_worker_name(queue)).work()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 135, in __init__
    self.validate_queues()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 179, in validate_queues
    raise TypeError('{0} is not of type {1} or text type'.format(queue, self.queue_class))
TypeError: long is not of type <class 'rq.queue.Queue'> or text type
    start_worker(queue)
  File "/home/test/frappe-bench/apps/frappe/frappe/utils/background_jobs.py", line 72, in start_worker
    Worker(queues, name=get_worker_name(queue)).work()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 135, in __init__
    self.validate_queues()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 179, in validate_queues
    raise TypeError('{0} is not of type {1} or text type'.format(queue, self.queue_class))
TypeError: default is not of type <class 'rq.queue.Queue'> or text type
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/home/test/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 79, in <module>
    main()
  File "/home/test/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 16, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 610, in __call__
    return self.main(*args, **kwargs)
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 590, in main
    rv = self.invoke(ctx)
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 936, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 936, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 782, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/click/core.py", line 416, in invoke
    return callback(*args, **kwargs)
  File "/home/test/frappe-bench/apps/frappe/frappe/commands.py", line 1040, in start_worker
    start_worker(queue)
  File "/home/test/frappe-bench/apps/frappe/frappe/utils/background_jobs.py", line 72, in start_worker
    Worker(queues, name=get_worker_name(queue)).work()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 135, in __init__
    self.validate_queues()
  File "/home/test/frappe-bench/env/local/lib/python2.7/site-packages/rq/worker.py", line 179, in validate_queues
    raise TypeError('{0} is not of type {1} or text type'.format(queue, self.queue_class))
TypeError: short is not of type <class 'rq.queue.Queue'> or text type 

Any idea what is causing this? Thanks.