[bugfix] Do not crash in case of broken pipe errors

[teojgo]

• Ignore the BrokenPipeError which is caused when
  the logging.Handler tries to emit to a closed stream.

Fixes #1201

[vkarak]

lgtm

[codecov-io]

Codecov Report

Merging #1257 into master will decrease coverage by 0.32%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #1257      +/-   ##
==========================================
- Coverage   91.42%   91.10%   -0.33%     
==========================================
  Files          84       84              
  Lines       12401    12000     -401     
==========================================
- Hits        11337    10932     -405     
- Misses       1064     1068       +4     

Impacted Files	Coverage Δ
reframe/core/logging.py	83.76% <50.00%> (-0.88%)	⬇️
reframe/core/modules.py	60.66% <0.00%> (-1.93%)	⬇️
reframe/core/deferrable.py	92.94% <0.00%> (-1.79%)	⬇️
reframe/core/systems.py	87.96% <0.00%> (-1.71%)	⬇️
unittests/test_launchers.py	92.72% <0.00%> (-1.48%)	⬇️
unittests/test_environments.py	72.07% <0.00%> (-1.22%)	⬇️
reframe/core/environments.py	88.28% <0.00%> (-1.09%)	⬇️
reframe/core/schedulers/__init__.py	94.73% <0.00%> (-0.75%)	⬇️
reframe/core/exceptions.py	85.07% <0.00%> (-0.75%)	⬇️
reframe/core/runtime.py	88.96% <0.00%> (-0.74%)	⬇️
... and 29 more

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