Infixowl cleanup iii

[ghost]

Maintenance-positive changes recommended by flake8-bugbear, mostly explicitly indicating unused loop variables with a prefixing underscore (it identiified one case where none of the loop variables were being used) and a couple of don't-use-mutable-objects-as-args instances.

Summary of changes

1. Added leading underscore to unused loop variables, removed mutable objects from args, (replacing with None and then performing an explicit “if None” assignment in the body of the method).

2. Swapped out an excessively weak, coverage-motivated length test of hash() (which was causing intermittent test failures) for an equality test of two runs, fixes issue Low probability failure in test/test_extras/test_infixowl/test_restriction.py::test_restriction_str_and_hash #2030

Checklist

• Checked that there aren't other open pull requests for the same change.
• Added tests for any changes that have a runtime impact.
• Checked that all tests and type checking passes.
• For changes that have a potential impact on users of this project:
  • Updated relevant documentation to avoid inaccuracies.
  • Considered adding additional documentation.
  • Considered adding an example in ./examples for new features.
  • Considered updating our changelog (CHANGELOG.md).
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[coveralls]

Coverage remained the same at 90.445% when pulling 867fe55 on gjhiggins:infixowl-cleanup-iii into 40eaa26 on RDFLib:master.

[aucampia]

LGMT, also updated the CHANGELOG.