Literal datetime sub

[ghost]

Summary of changes

rebased PR #1089 from 2 yrs ago, adding DateTime arithmetic operations for Literals - an extension of #629, additional tests of numerics added, as requested in #1089 (comment) and limited modernisation of test/test_literal/test_literal.py

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.

[aucampia]

@gjhiggins I added some more tests and fixed some issues in this PR against your branch: https://github.com/gjhiggins/rdflib/pull/7

[ghost]

@gjhiggins I added some more tests and fixed some issues in this PR against your branch: gjhiggins#7

Thanks for the support, looking good.

[aucampia]

LGTM, one small concern is some logic that is in __add__ (and carried over to __sub__) from before, but I think it makes sense to have these methods behave the same in these regards so I'm okay with it.

[coveralls]

Coverage increased (+0.01%) to 88.41% when pulling a79599e on gjhiggins:literal-datetime-sub into 8a096ab on RDFLib:master.

[aucampia]

Resolving conflicts

[aucampia]

Resolving conflicts

Done.

[aucampia]

@RDFLib/core I will merge this by 2022-05-17 if there is no further feedback.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[aucampia]

Merging this with only one approval because the change is well tested and the addition of __sub__ make sense as we are already providing __add__.