Logging fix using global QueueHandler

[mraspaud]

It has been observed that trollflow2 v0.11.0 hangs quite often, probably due to a race condition in the logging code.

It is very likely that this bug has been introduced in #115, hence this attempt to make the QueueHandler usage more streamlined, independently of whether trollflow2 runs on threads or subprocesses, and more importantly by setting up the queued log handler and other handlers prior to running the main loop.

EDIT: for completeness, it should be noted that many live tests have been run with v0.10.0 at SMHI and that hanging specifically in the logging part was also happening.

• [x] Tests added
• [x] Tests passed
• [x] Live test ran several days without crashing
• [x] Fully documented

[codecov[bot]]

Codecov Report

Merging #124 (1a63f48) into main (582852b) will decrease coverage by 0.39%. The diff coverage is 91.78%.

@@            Coverage Diff             @@
##             main     #124      +/-   ##
==========================================
- Coverage   95.10%   94.70%   -0.40%     
==========================================
  Files           9       11       +2     
  Lines        2125     2211      +86     
==========================================
+ Hits         2021     2094      +73     
- Misses        104      117      +13     

Flag	Coverage Δ
unittests	94.70% <91.78%> (-0.40%)	:arrow_down:

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Impacted Files	Coverage Δ
trollflow2/launcher.py	86.11% <79.10%> (-3.14%)	:arrow_down:
trollflow2/tests/test_launcher.py	97.86% <95.08%> (-0.80%)	:arrow_down:
trollflow2/logging.py	100.00% <100.00%> (ø)
trollflow2/plugins/__init__.py	91.82% <100.00%> (ø)
trollflow2/tests/test_logging.py	100.00% <100.00%> (ø)

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