Fixed legacy_windows is auto-detected as True incorrectly, when not in terminal environment

[xymy]

Type of changes

• Bug fix
• New feature
• Documentation / docstrings
• Tests
• Other

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review.

Description

Fix #3647

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.25%. Comparing base (02f3d14) to head (b9b2ca3).
⚠️ Report is 135 commits behind head on master.
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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3648   +/-   ##
=======================================
  Coverage   98.25%   98.25%           
=======================================
  Files          74       74           
  Lines        8095     8101    +6     
=======================================
+ Hits         7954     7960    +6     
  Misses        141      141           

Flag	Coverage Δ
unittests	98.25% <100.00%> (+<0.01%)	⬆️

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