refactor: use pathlib in util.py

[miles170]

Closes #1983.

[codecov-commenter]

Codecov Report

Merging #2024 (a8c782c) into main (b6632d6) will decrease coverage by 6.77%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2024      +/-   ##
==========================================
- Coverage   85.04%   78.26%   -6.78%     
==========================================
  Files         335      335              
  Lines        7583     7583              
  Branches      989      989              
==========================================
- Hits         6449     5935     -514     
- Misses        861     1391     +530     
+ Partials      273      257      -16     

Flag	Coverage Δ
longtests	78.26% <ø> (+0.18%)	⬆️
win-longtests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
test/test_requirements.py	0.00% <0.00%> (-89.88%)	⬇️
cve_bin_tool/nvd_api.py	24.00% <0.00%> (-52.80%)	⬇️
test/test_nvd_api.py	50.87% <0.00%> (-40.36%)	⬇️
test/test_source_nvd.py	60.71% <0.00%> (-39.29%)	⬇️
test/test_scanner.py	60.13% <0.00%> (-34.27%)	⬇️
test/test_source_osv.py	68.85% <0.00%> (-31.15%)	⬇️
cve_bin_tool/checkers/xml2.py	61.36% <0.00%> (-27.28%)	⬇️
cve_bin_tool/data_sources/nvd_source.py	29.18% <0.00%> (-26.49%)	⬇️
test/test_source_gad.py	73.68% <0.00%> (-24.57%)	⬇️
test/test_available_fix.py	76.47% <0.00%> (-23.53%)	⬇️
... and 19 more

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[terriko]

Windows tests failing is a known issue: (#2038) so this looks ready to go. Thank you and happy hacktoberfest!