Return the exit code instead of exiting in main

[Schamper]

Noticed this while browsing this file looking for a way to do something.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 47.37%. Comparing base (1b3e67c) to head (6930f1b).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
acquire/tools/decrypter.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #211   +/-   ##
=======================================
  Coverage   47.37%   47.37%           
=======================================
  Files          26       26           
  Lines        3466     3466           
=======================================
  Hits         1642     1642           
  Misses       1824     1824           

Flag	Coverage Δ
unittests	47.37% <50.00%> (ø)

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