Reduce test warnings

[pnuu]

This PR aims at reducing warnings emitted when running the tests.

Needs rebasing after #201 has been merged.

• Closes #xxxx
• Tests added
• Tests passed
• Passes flake8 trollflow2
• Fully documented
• Add your name to AUTHORS.md if not there already

[pnuu]

I'm not actually sure we can start using timezone-aware datetimes before Satpy and everything else is doing that.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.86%. Comparing base (146757d) to head (643b5c7).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #202      +/-   ##
==========================================
+ Coverage   95.80%   95.86%   +0.06%     
==========================================
  Files          13       13              
  Lines        3000     3000              
==========================================
+ Hits         2874     2876       +2     
+ Misses        126      124       -2     

Flag	Coverage Δ
unittests	95.86% <100.00%> (+0.06%)	⬆️

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[pnuu]

See also pytroll/satpy#2752

[pnuu]

For Python 3.12 the number of warnings dropped from 897 to 17 (locally, 16 on CI where there's a newer dateutils). For 3.11 the figures are 880 -> 4 (5 in CI, can't spot where the difference is).

The AttributeError: 'NoneType' object has no attribute 'setsockopt' needs to be fixed in Posttroll.

[pnuu]

The leftover warnings:

trollflow2/tests/test_trollflow2.py::TestFilePublisher::test_filepublisher_with_compose
trollflow2/tests/test_trollflow2.py::TestFilePublisher::test_filepublisher_without_compose
  /home/lahtinep/mambaforge/envs/py311/lib/python3.11/site-packages/_pytest/unraisableexception.py:78: PytestUnraisableExceptionWarning: Exception ignored in: <function FilePublisher.__del__ at 0x7ceffb6184a0>
  
  Traceback (most recent call last):
    File "/home/lahtinep/Software/pytroll/pytroll_packages/trollflow2/trollflow2/plugins/__init__.py", line 560, in __del__
      self.stop()
    File "/home/lahtinep/Software/pytroll/pytroll_packages/trollflow2/trollflow2/plugins/__init__.py", line 555, in stop
      self.pub.stop()
    File "/home/lahtinep/Software/pytroll/pytroll_packages/posttroll/posttroll/publisher.py", line 144, in stop
      self.publish_socket.setsockopt(zmq.LINGER, 1)
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  AttributeError: 'NoneType' object has no attribute 'setsockopt'

Easy to get rid off by adding if self.publish.socket: in posttroll.publisher.Publisher.stop, which I tested locally and works for this. I'm not sure why the patching in posttroll.testing.patched_publisher doesn't already handle this.

[pnuu]

The warning about losing projection information was actually coming from area_def.proj_dict usage in Trollflow2. This is now replaced with area_def.is_geostationary and the only leftover warnings are the above setsockopt and the few timezone awareness warnings from other libraries for Python 3.12.