Error unpacking ReasonCodes in Python2.7

Hello there,

I've got a test that used to run fine with paho-mqtt 1.5.1 on Python 2.7 but now it's failing. Here's the traceback:

  [irrelevant frames]
   client.loop()
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 1120, in loop
    return self._loop(timeout)
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 1164, in _loop
    rc = self.loop_read()
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 1556, in loop_read
    rc = self._packet_read()
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 2439, in _packet_read
    rc = self._packet_handle()
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 3045, in _packet_handle
    return self._handle_disconnect()
  File "c:\...\eggs\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\client.py", line 3220, in _handle_disconnect
    reasonCode.unpack(self._in_packet['packet'])
  File "c:\...\paho_mqtt-1.6.1-py2.7.egg\paho\mqtt\reasoncodes.py", line 166, in unpack
    c = ord(c)
TypeError: ord() expected string of length 1, but int found

Here's the body of unpack:

def unpack(self, buffer):
    c = buffer[0]
    if sys.version_info[0] < 3:
        c = ord(c)
    name = self.__getName__(self.packetType, c)
    self.value = self.getId(name)
    return 1

Apparently the reason for this problem is that the argument buffer used to be a bytes object (or str in Python2) on version 1.5.1 but now it's a bytearray... which causes buffer[0] to return an int instead of a str/bytes object with length of 1... and then subsequently the call to ord fails. Here where the type was defined on 1.5.1, and here on 1.6.1.

The solution seems clear to me: remove the if sys.version_info[0] < 3: branch, as there is no need to check if python2 or 3 if we've got already an int.

I dont think we should focus on this issue due to the sunset of Python 2

https://www.python.org/doc/sunset-python-2/

There is already an issue for dropping support: https://github.com/eclipse/paho.mqtt.python/issues/279

Reasonable, although it makes my life a little harder on the short term.

I guess the next necessary step would be to drop support officially, i.e. update the README, drop python2 package classifiers, etc.

Closing due to inactivity and because it should be covered by #279 (probably should have dropped Python 2 support some time ago!). This is part of a general project to clean-up issues (which should make it simpler to identify priorities going forward).