Small updates and fixes

[s0undt3ch]

• Don't set the config value twice for the same marker
• Update copyright headers
• Also capture stderr so that no errors are seen on console

[codecov]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (7665312) 93.09% compared to head (daec41a) 96.85%.
Report is 52 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #33      +/-   ##
==========================================
+ Coverage   93.09%   96.85%   +3.76%     
==========================================
  Files          43       48       +5     
  Lines        1605     2058     +453     
==========================================
+ Hits         1494     1993     +499     
+ Misses        111       65      -46     

Flag	Coverage Δ
Linux	98.45% <99.22%> (+3.50%)	⬆️
Py35	?
Py36	?
Py37	?
Py38	?
Py39	?
PyTest60	?
PyTest61	?
PyTest62	?
Windows	96.02% <98.47%> (+4.00%)	⬆️
macOS	98.45% <99.22%> (+3.50%)	⬆️
py3.10	96.85% <98.47%> (?)
py3.7	96.83% <98.47%> (?)
py3.8	96.75% <98.47%> (?)
py3.9	96.75% <98.47%> (?)
pytest-7.1.0	98.45% <99.22%> (?)
pytest-7.2.0	98.45% <99.22%> (?)
pytest-7.3.0	96.85% <98.47%> (?)
pytest-7.4.0	96.85% <98.47%> (?)
src	91.00% <95.38%> (+7.95%)	⬆️
tests	100.00% <100.00%> (ø)

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Files	Coverage Δ
src/pytestskipmarkers/__init__.py	100.00% <ø> (ø)
src/pytestskipmarkers/plugin.py	100.00% <100.00%> (ø)
src/pytestskipmarkers/utils/platform.py	100.00% <100.00%> (ø)
src/pytestskipmarkers/utils/ports.py	61.12% <100.00%> (+1.12%)	⬆️
src/pytestskipmarkers/utils/socket.py	100.00% <ø> (ø)
tests/conftest.py	100.00% <100.00%> (ø)
tests/functional/test_destructive_test.py	100.00% <ø> (ø)
tests/functional/test_expensive_test.py	100.00% <100.00%> (ø)
tests/functional/test_requires_network.py	100.00% <100.00%> (ø)
tests/functional/test_skip_if_binaries_missing.py	100.00% <100.00%> (ø)
... and 38 more