Remove usage of unittest testcase

[pnuu]

I got annoyed by a directory named "örülök, hogy megismerhetem" being created in the repository directory. While hunting why it wasn't removed automatically, I ended up removing the usage of unittest.TestCase from the tests. Also use of single quotes is replaced with double quotes.

• Closes #xxxx
• Tests added
• Tests passed
• Passes flake8 trollflow2
• Fully documented
• Add your name to AUTHORS.md if not there already

[mraspaud]

Thanks a lot for taking this up, and it looks good so far...

[pnuu]

The problem was simply that I didn't notice one tear-down method and renaming it solved the race conditions. At least it did locally...

[codecov]

Codecov Report

❌ Patch coverage is 97.22222% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.52%. Comparing base (1eff3b7) to head (bec2e28).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
trollflow2/tests/test_launcher.py	98.09%	2 Missing ⚠️
trollflow2/tests/utils.py	84.61%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #242      +/-   ##
==========================================
- Coverage   94.75%   94.52%   -0.23%     
==========================================
  Files          15       15              
  Lines        3373     3379       +6     
==========================================
- Hits         3196     3194       -2     
- Misses        177      185       +8     

Flag	Coverage Δ
unittests	94.52% <97.22%> (-0.23%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[mraspaud]

LGTM!