Unable to update trade request

[icook]

We get these pretty regularly for a short time and they're cluttering Sentry.

Stacktrace (most recent call last):

  File "simplecoin/rpc_views.py", line 91, in update_trade_requests
    tr.distribute()
  File "simplecoin/models.py", line 86, in distribute
    amounts = distributor(payable_amount, portions)
  File "simplecoin/scheduler.py", line 499, in distributor
    return _distributor(*args, **kwargs)
  File "simplecoin/scheduler.py", line 537, in _distributor
    assert abs(amount - new_amount) < (amount / 10000)