Integrate linter: flake8

[michaeldiamant]

Problem

A linter like flake8 catches issues like unused imports, and lack of adherence to language standards. It's ideal to catch these issues during the CI process because it provides a consistent approach to writing software in all parts of a repo.

Solution

While multiple linters exist, I propose starting with flake8 and later swapping out and/or adding others. #213 illustrates partial integration and can be extended.

A full solution includes:

• CI process runs flake8.
• Ensure CI and local building share the same steps.
  • Presumably, a script can be written to accomplish the goal. I'm being vague to allow freedom for interpretation.
• Upon merge, flake8 does not find errors. Implies fixing errors for the to-be-agreed upon flake8 configuration.
• Add pyteal repo docs explaining flake8 usage.

Dependencies

N/A

Urgency

[michaeldiamant]

Presuming minimum Python version >= 3.7, it might be prudent to consider https://docs.python.org/3/library/devmode.html.

[michaeldiamant]

Consider https://github.com/bndr/pipreqs to isolate unused dependencies. Thanks to @tzaffi for suggesting in #249 (comment).

[tzaffi]

That's a fine idea. Upon further investigation, one contender to pipreqs is pigar. It seems more active than pipreqs, if not as polished.

[michaeldiamant]

FYI - I opened an issue to tracking monitoring unused dependencies because we didn't tackle it here: #298.