pserv is oopsing: "exceptions.TypeError: not all arguments converted during string formatting"

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/twisted/python/log.py", line 69, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 118, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 81, in callWithContext
    return func(*args,**kw)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/posixbase.py", line 626, in _doReadOrWrite
    why = selectable.doRead()
--- <exception caught here> ---
  File "/usr/lib/python2.7/dist-packages/twisted/internet/udp.py", line 147, in doRead
    self.protocol.datagramReceived(data, addr)
  File "/usr/lib/python2.7/dist-packages/tftp/bootstrap.py", line 173, in datagramReceived
    return self.tftp_ERROR(datagram)
  File "/usr/lib/python2.7/dist-packages/tftp/bootstrap.py", line 183, in tftp_ERROR
    log.msg("Got error: " % datagram)
exceptions.TypeError: not all arguments converted during string formatting