Fix inconsistent error messages involving output-file

[twiggler]

Note: There are failing CI checks unrelated to this pr. After CI is fixed, this PR can be re-reviewed.

Make error messages concerning output-file consistent with the name of the flag.

extra:

• git ignore acquire artifacts when running the package from the root.
• fully git ignore the .tox directory

closes #169

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.60%. Comparing base (16f8afa) to head (e48041d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #191   +/-   ##
=======================================
  Coverage   44.60%   44.60%           
=======================================
  Files          26       26           
  Lines        3394     3394           
=======================================
  Hits         1514     1514           
  Misses       1880     1880           

Flag	Coverage Δ
unittests	44.60% <100.00%> (ø)

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[Miauwkeru]

these are only artifacts generate from where you run acquire. These do not need to be ignored as they are not build artifacts.

[twiggler]

I will move these to my local exclude file.

[Miauwkeru]

Could you adjust the title of the PR to be a bit more informative of what it changes? And so it adheres to https://docs.dissect.tools/en/latest/contributing/style-guide.html