fix: pre_install/post_install receiving a generator not a list

[PKilcommons]

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

Fixes #3190

I wasn't so sure about where it made the most sense to put the regression tests so let me know if there's a more sensible place for them, or if you have a better idea for how they should be written.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.63%. Comparing base (d579492) to head (fdfe3dd).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3191   +/-   ##
=======================================
  Coverage   85.63%   85.63%           
=======================================
  Files         112      112           
  Lines       11213    11213           
  Branches     2432     2432           
=======================================
  Hits         9602     9602           
  Misses       1098     1098           
  Partials      513      513           

Flag	Coverage Δ
unittests	85.43% <100.00%> (ø)

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[frostming]

thanks