def claim(task, force = false)
      raise UnauthorizedClaimAttempt unless has_role?(task.role)
      release!(task) if force
      task.claim(claim_token)
    end
def claim(task, force = false)
      raise UnauthorizedClaimAttempt unless has_role?(task.role)
      release!(task) if force
      task.claim(claim_token)
    end
Attempts to set self as the claimant of the given task.  If not authorized
 to claim the task, raises exception.  Also bubbles exception from Task
 when task is already claimed by a different claimant.