CI: handle subprocess for windows

[cadenmyers13]

This wasn't passing CI on windows, so hopefully this works with this fix.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.47%. Comparing base (79170b1) to head (80241d2).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #72      +/-   ##
==========================================
+ Coverage   92.39%   92.47%   +0.08%     
==========================================
  Files           3        3              
  Lines         184      186       +2     
==========================================
+ Hits          170      172       +2     
  Misses         14       14              

Files with missing lines	Coverage Δ
tests/test_packsmanager.py	95.04% <100.00%> (+0.10%)	⬆️

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[cadenmyers13]

@sbillinge ready for review

[sbillinge]

This wasn't passing CI on windows, so hopefully this works with this fix.

Let's try

[cadenmyers13]

@sbillinge it passed 🙏