Issue #402: Fix tests that fail as a result of running `pytest` with no flags

[baileythegreen]

CLI parsing in pyani_script.py and some test files made the implicit assumption that they were dealing with a pyani command; however, these files also parse the command line when a pytest command is issued. When:

$ pytest

is run on its own (with no flags), this therefore caused things to fail.

Closes #402.

Type of change

• [X] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality not to work as expected)
• [ ] This change requires a documentation update
• [ ] This is a documentation update

Action Checklist

• [X] Work on a single issue/concept (if there are multiple separate issues to address, please use a separate pull request for each)
• [ ] Fork the pyani repository under your own account (please allow write access for repository maintainers)
• [X] Set up an appropriate development environment (please see CONTRIBUTING.md)
• [X] Create a new branch with a short, descriptive name
• [X] Work on this branch
  • [X] style guidelines have been followed
  • [X] new code is commented, especially in hard-to-understand areas
  • [ ] corresponding changes to documentation have been made
  • [ ] tests for the change have been added that demonstrate the fix or feature works
• [X] Test locally with pytest -v non-passing code will not be merged
• [X] Rebase against origin/master
• [X] Check changes with flake8 and black before submission
• [X] Commit branch
• [X] Submit pull request, describing the content and intent of the pull request
• [ ] Request a code review
• [ ] Continue the discussion at Pull requests section in the pyani repository

[codecov[bot]]

Codecov Report

Merging #404 (5676e63) into master (62949c4) will decrease coverage by 0.00%. The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master     #404      +/-   ##
==========================================
- Coverage   75.82%   75.81%   -0.01%     
==========================================
  Files          55       55              
  Lines        3747     3750       +3     
==========================================
+ Hits         2841     2843       +2     
- Misses        906      907       +1     

[baileythegreen]

Sorry, I missed there were comments on this the other day; I only saw the email about codecov.