Retry upon test failure if in Windows

[tkf]

Workaround #462, which is frequent enough to be troublesome.

[codecov]

Codecov Report

Merging #468 (529cd76) into master (a5290c4) will increase coverage by 0.14%.
The diff coverage is 97.50%.

@@            Coverage Diff             @@
##           master     #468      +/-   ##
==========================================
+ Coverage   89.04%   89.19%   +0.14%     
==========================================
  Files          39       39              
  Lines        2273     2313      +40     
==========================================
+ Hits         2024     2063      +39     
- Misses        249      250       +1     

Impacted Files	Coverage Δ
src/julia/tests/utils.py	97.14% <95.23%> (-2.86%)	⬇️
src/julia/tests/test_core.py	99.03% <100.00%> (+0.03%)	⬆️
src/julia/tests/test_libjulia.py	100.00% <100.00%> (ø)
src/julia/tests/test_utils.py	100.00% <100.00%> (ø)

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