TST: Add pytest-flake8 to travis tests

[jklenzing]

Description

Adds flake8 testing to the Travis CI tests.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

How Has This Been Tested?

Tested via Travis CI.

Checklist:

• Make sure you are merging into the develop (not master) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to CHANGELOG.md, summarizing the changes

Notes

• W503 and W504 (line breaks and operators) are mutually exclusive. Ignoring W503 to better match PEP8 standards.

[jklenzing]

Leaving code as is to show how the interface works. Current flake8 issues listed here (starting at line 750): https://travis-ci.org/github/pysat/pysatModels/jobs/677321154

[aburrell]

The only problem I am not sure how to solve is the 'import not used' when importing things with __init__.py.

[jklenzing]

The only problem I am not sure how to solve is the 'import not used' when importing things with __init__.py.

Two ways of solving this:

• In sami2py, we've added # noqa: F401 as a comment to each of the import lines. This tells flake8 that we have decided to skip F401 on this line only (noqa == no quality assurance)
• A global ignore for F401 can be added, though this will turn this off everywhere,

Poking around in other packages, the noqa route seems to be the one to take, which is why we used it in sami2py.

[aburrell]

I'd like the contributing documentation to be improved. Doing it myself in the next commit.

[aburrell]

Ok, I had to make a compromise with the CONTRIBUTING.md rendering. Eventually this may be improved: miyakogi/m2r#53.

[aburrell]

@jklenzing @rstoneback @asher-pembroke : you all may want to take a look at the changes I made to the CONTRIBUTING.md file, given that this was likely copy-pasted from pysat and therefore the same changes may be useful there (and in the other pysat projects).

[jklenzing]

Some weird formatting stuff in readthedocs for contributing:
https://pysatmodels.readthedocs.io/en/flake8/develop_guide/contributing.html

I wonder if we should just use rst instead of markdown for the contributing doc to aid in the import.

[aburrell]

Yes, that's the issue I referenced above. I think it would be simpler all around to switch to RST, especially since GitHub has its own flavour of markdown.