BUG: Fix os error on MacOS

[ChengjieLi28]

What do these changes do?

Related issue number

Fixes #18

Check code requirements

• [ ] tests added / passed (if needed)
• [ ] Ensure all linting tests pass

[codecov[bot]]

Codecov Report

Merging #19 (b472f54) into main (a66fafd) will increase coverage by 0.15%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
+ Coverage   90.98%   91.13%   +0.15%     
==========================================
  Files          42       42              
  Lines        3207     3205       -2     
  Branches      641      641              
==========================================
+ Hits         2918     2921       +3     
+ Misses        215      209       -6     
- Partials       74       75       +1     

Flag	Coverage Δ
unittests	90.98% <100.00%> (+0.15%)	:arrow_up:

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

Impacted Files	Coverage Δ
python/xoscar/constants.py	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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