when USB connection fails, sound alarm and/or open dialog

[astraw]

I sometimes am getting this error:

Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/motmot/fview_ext_trig/fview_ext_trig.py", line 319, in OnTimer
    self.timestamp_modeler.update()
  File "/usr/lib/pymodules/python2.6/motmot/fview_ext_trig/live_timestamp_modeler.py", line 224, in update
    results = self._get_now_framestamp(full_output=return_last_measurement_info)
  File "/usr/lib/pymodules/python2.6/motmot/fview_ext_trig/live_timestamp_modeler.py", line 176, in _get_now_framestamp
    results = self._trigger_device.get_framestamp(full_output=full_output)
  File "/usr/lib/pymodules/python2.6/motmot/fview_ext_trig/ttrigger.py", line 402, in get_framestamp
    self._send_buf(buf)
  File "/usr/lib/pymodules/python2.6/motmot/fview_ext_trig/ttrigger.py", line 562, in _send_buf
    val = usb.bulk_write(self._libusb_handle, 0x06, buf, 9999)
  File "/usr/lib/pymodules/python2.6/pylibusb/pylibusb.py", line 466, in bulk_write
    buf, len(buf), timeout))
  File "/usr/lib/pymodules/python2.6/pylibusb/pylibusb.py", line 453, in CHK
    raise exc_class("%d: %s"%(result,errstr))
pylibusb.pylibusb.USBNoDataAvailableError: -110: could not get bound driver: No data available

Of course this should get fixed. In addition to fixing it, however, we should notify the user (with a sound and/or dialog) if it happens.