JSONDecodeError in rabbitmq.list_user_permissions

Description of Issue

There seems to be a compatibility issue or regression of some sort in Salt 3004 on Ubuntu Server 18.04 LTS with RabbitMQ 3.6.10 (from Ubuntu repository) where the rabbitmq.list_user_permissions module throws a JSONDecodeError exception.

I dug through the release notes and found that the dependency on the --formatter=json flag was introduced as part of the solution to issue #49115 . That fix is great, but I believe the issue is that older versions of rabbitmqctl don't support the --formatter=json option.

I wasn't able to easily determine in the RabbitMQ release notes when the flag was added to rabbitmqctl. I can probably figure it out, but getting a little cross-eyed tonight from looking at other unrelated issues before I hit this one.

My personal workaround is to drop back to < 3004 until my next opportunity to upgrade RabbitMQ since I'm stuck running against these packages for a while. I'm logging mainly to help clarify if the intention was to drop support for older RabbitMQ releases that might still be common in the wild and to give other folks a search result if they run into the same conundrum during a Salt upgrade.

Results from 3003.3:

$ salt --version
salt 3003.3

$ salt-call rabbitmq.list_user_permissions admin
local:
    ----------
    /:
        - .*
        - .*
        - .*

Results from 3004:

$ salt --version
salt 3004

$ salt-call rabbitmq.list_user_permissions admin
[ERROR   ] stderr: Error: operation list_user_permissions used with invalid parameter: ["admin",
                                                                     "--formatter=json"]
[ERROR   ] retcode: 64
[ERROR   ] An un-handled exception was caught by salt's global exception handler:
JSONDecodeError: Expecting value: line 1 column 1 (char 0)
Traceback (most recent call last):
  File "/usr/bin/salt-call", line 11, in <module>
    load_entry_point('salt==3004', 'console_scripts', 'salt-call')()
  File "/usr/lib/python3/dist-packages/salt/scripts.py", line 432, in salt_call
    client.run()
  File "/usr/lib/python3/dist-packages/salt/cli/call.py", line 55, in run
    caller.run()
  File "/usr/lib/python3/dist-packages/salt/cli/caller.py", line 111, in run
    ret = self.call()
  File "/usr/lib/python3/dist-packages/salt/cli/caller.py", line 219, in call
    self.opts, data, func, args, kwargs
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 149, in __call__
    return self.loader.run(run_func, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1201, in run
    return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/contextvars/__init__.py", line 38, in run
    return callable(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1216, in _run_as
    return _func_or_method(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/executors/direct_call.py", line 10, in execute
    return func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 149, in __call__
    return self.loader.run(run_func, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1201, in run
    return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/contextvars/__init__.py", line 38, in run
    return callable(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/loader/lazy.py", line 1216, in _run_as
    return _func_or_method(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/salt/modules/rabbitmq.py", line 698, in list_user_permissions
    perms = salt.utils.json.loads(res["stdout"])
  File "/usr/lib/python3/dist-packages/salt/utils/json.py", line 89, in loads
    return json_module.loads(s, **kwargs)
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Setup

• Set up a rabbitmq user

Steps to Reproduce Issue

$ salt-call rabbitmq.list_user_permissions admin

Versions Report

Salt Version:
          Salt: 3004

Dependency Versions:
          cffi: Not Installed
      cherrypy: Not Installed
      dateutil: 2.6.1
     docker-py: Not Installed
         gitdb: 2.0.3
     gitpython: 2.1.8
        Jinja2: 2.10
       libgit2: Not Installed
      M2Crypto: Not Installed
          Mako: Not Installed
       msgpack: 0.5.6
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: Not Installed
      pycrypto: 2.6.1
  pycryptodome: 3.4.7
        pygit2: Not Installed
        Python: 3.6.9 (default, Jan 26 2021, 15:33:00)
  python-gnupg: 0.4.1
        PyYAML: 3.12
         PyZMQ: 17.1.2
         smmap: 2.0.3
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.2.5

System Versions:
          dist: ubuntu 18.04 Bionic Beaver
        locale: UTF-8
       machine: x86_64
       release: 4.15.0-156-generic
        system: Linux
       version: Ubuntu 18.04 Bionic Beaver

Start in salt/modules/rabbitmq.py at list_user_permissions, where the reported JSONDecodeError occurs, and reproduce the command against RabbitMQ 3.6.10. Check how the unsupported --formatter=json response is handled; done means the module no longer raises JSONDecodeError and returns permissions or a clear compatibility error for this RabbitMQ version.