Warnings generated from hwp supervisor tests

[BrianJKoopman]

Noticed these while reviewing #824 (though it happens without that change too):

$ python -m pytest --cov --cov-report html integration/test_hwp_supervisor_agent_integration.py
======================================================== test session starts ========================================================
platform linux -- Python 3.11.9, pytest-8.3.4, pluggy-1.5.0
rootdir: /home/koopman/git/socs/tests
configfile: pytest.ini
plugins: order-1.3.0, dependency-0.6.0, cov-6.0.0, twisted-1.14.3, docker-3.1.2
collected 2 items

integration/test_hwp_supervisor_agent_integration.py ..                                                                       [100%]

========================================================= warnings summary ==========================================================
integration/test_hwp_supervisor_agent_integration.py::test_supervisor_grip
integration/test_hwp_supervisor_agent_integration.py::test_hwp_spinup
  /home/koopman/virtualenvs/3.11/lib/python3.11/site-packages/_pytest/threadexception.py:82: PytestUnhandledThreadExceptionWarning: Exception in thread background

  Traceback (most recent call last):
    File "/home/koopman/git/socs/socs/testing/hwp_emulator.py", line 346, in process_pcu_msg
      _, cmd, chan_str = data.split(" ")
      ^^^^^^^^^^^^^^^^
  ValueError: not enough values to unpack (expected 3, got 1)

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File "/home/koopman/.pyenv/versions/3.11.9/lib/python3.11/threading.py", line 1045, in _bootstrap_inner
      self.run()
    File "/home/koopman/.pyenv/versions/3.11.9/lib/python3.11/threading.py", line 982, in run
      self._target(*self._args, **self._kwargs)
    File "/home/koopman/git/socs/socs/testing/device_emulator.py", line 205, in _read_serial
      response = self.get_response(msg)
                 ^^^^^^^^^^^^^^^^^^^^^^
    File "/home/koopman/git/socs/socs/testing/hwp_emulator.py", line 349, in process_pcu_msg
      raise ValueError(f"Unable to parse message: {data}")
  ValueError: Unable to parse message:

    warnings.warn(pytest.PytestUnhandledThreadExceptionWarning(msg))

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

---------- coverage: platform linux, python 3.11.9-final-0 -----------
Coverage HTML written to dir htmlcov

I didn't dig into them, but wanted to note them.