Communication issues from master to minion using 2019.2

[Skeen]

Hi,

I'm seeing issues with master --> minion communication using 2019.2.
I'm not seeing these issues using 2018.3.

Steps to reproduce:

1. Start salt using, docker-compose up -d:

root@dev:/opt/docker/saltmaster# cat docker-compose.yml 
version: '3'
services:
  saltmaster:
    container_name: salt-master
    image: saltstack/salt:2019.2
    ports:
      - "4505:4505"
      - "4506:4506"
    restart: unless-stopped

root@dev:/opt/docker/saltmaster# docker-compose up -d
Starting salt-master ... done

2. Connect a minion to the master.
3. Accept the minion on the master, using salt-key -Ay:

root@dev:/opt/docker/saltmaster# sudo docker exec -it salt-master salt-key -Ay
The following keys are going to be accepted:
Unaccepted Keys:
minion_id_here
Key for minion minion_id_here accepted.

4. Validate minion --> master communication using salt-call:

vagrant@node-3:~$ sudo salt-call test.ping
local:
    True

5. Validate master --> minion communication using salt:

root@dev:/opt/docker/saltmaster# sudo docker exec -it salt-master salt '*' test.ping
minion_id_here:
    Minion did not return. [No response]
ERROR: Minions returned with non-zero exit code

The expected output here, would be similar to what I get with 2018.3:

root@dev:/opt/docker/saltmaster# sudo docker exec -it salt-master salt '*' test.ping
[WARNING ] /usr/lib/python3.7/site-packages/salt/transport/ipc.py:280: DeprecationWarning: encoding is deprecated, Use raw=False instead.
  self.unpacker = msgpack.Unpacker(encoding=encoding)

[WARNING ] /usr/lib/python3.7/site-packages/salt/payload.py:145: DeprecationWarning: encoding is deprecated, Use raw=False instead.
  ret = msgpack.loads(msg, use_list=True, ext_hook=ext_type_decoder, encoding=encoding)

minion_id_here:
    True

The salt-master log has the following error message within it (on 2019.2):

root@dev:/opt/docker/saltmaster# sudo docker logs salt-master
...
Process salt.transport.zeromq.<class 'method'>._publish_daemon:
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/multiprocessing/process.py", line 297, in _bootstrap
    self.run()
  File "/usr/local/lib/python3.7/multiprocessing/process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/local/lib/python3.7/site-packages/salt/transport/zeromq.py", line 908, in _publish_daemon
    unpacked_package = salt.payload.unpackage(package)
  File "/usr/local/lib/python3.7/site-packages/salt/payload.py", line 89, in unpackage
    return msgpack.loads(package_, use_list=True)
  File "msgpack/_unpacker.pyx", line 195, in msgpack._cmsgpack.unpackb
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x83 in position 0: invalid start byte

I believe the relevant issue might be saltstack/salt#56007