====== Bug - unpack requires string argument length of 2 ======

<code>
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]: Traceback (most recent call last):
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:   File "gateway_server.py", line 81, in <module>
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:     xbg.begin_test(1,t_flag,kill_flag)
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:   File "/home/scel/control-tower/gateway/src/xbee_gateway.py", line 63, in begin_test
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:     callback(data, timestamp)
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:   File "/home/scel/control-tower/gateway/src/decoder.py", line 63, in decode_data
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:     if self.check_schema(data):
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:   File "/home/scel/control-tower/gateway/src/decoder.py", line 37, in check_schema
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]:     self.schema_num = struct.unpack('<' + 'H', data[0:2])[0]
Nov 11 15:21:39 scelserver-1 run_production.sh[28059]: struct.error: unpack requires a string argument of length 2
</code>