Replace os.path with pathlib

[c-w]

This pull request refactors all references to os.path to use the new pathlib module.

This makes the code a lot more natural to read. See PEP 428 for more information on why pathlib is a desirable improvement over the more low-level os.path.

All Submissions:

• Have you followed the guidelines in our Contributing document?

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

• Does your PR follow our Code of Conduct?

• Have you added an explanation of what your changes do and why you'd like us to include them?

• Does each method or function "do one thing well"? Reviewers may recommend methods be split up for maintainability and testability. Not applicable: pure refactor

• Is this code designed to be testable? Not applicable: pure refactor

• Is the code documented well? Not applicable: pure refactor

• Does your submission pass existing tests (or update existing tests with documentation regarding the change)? Docker build passes

• Have you added tests to cover your changes? Not applicable: pure refactor

• Have you linted your code prior to submission? Docker build passes

• Have you updated the documentation and README? Not applicable: pure refactor

• Is PII treated correctly? In particular, make sure the code is not logging objects or strings that might contain PII (e.g. request headers). Not applicable: none included

• Have secrets been stripped before committing? Not applicable: none included

[c-w]

@sayar There seems to be something wrong with the CI definition for the cli and app.

The build here fails, but running the Dockerfile locally succeeds with docker build -t agogosml/cli -f agogosml_cli/Dockerfile agogosml_cli (see screenshot below). So the CI fail here should not be considered a blocker.

[sayar]

LOVE IT!