Fix argument parser errors are printed without a trailing newline

[hhatto]

ref: #713

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.96%. Comparing base (c55f3e0) to head (02592cc).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #758   +/-   ##
=======================================
  Coverage   97.96%   97.96%           
=======================================
  Files           1        1           
  Lines        2460     2463    +3     
=======================================
+ Hits         2410     2413    +3     
  Misses         50       50           

Flag	Coverage Δ
3.11	97.52% <100.00%> (+<0.01%)	⬆️
3.12	97.80% <100.00%> (+<0.01%)	⬆️

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