Have lint run on __init__.py files

[dsherry]

This would protect us against typos and errors in those files. Currently we ignore them in our linting. I think there's a potential for defining circular imports as well, and I'm not sure how python reacts to that in these files.

[gsheni]

@dsherry the reason Featuretools avoids linting __init__.py files is because of this:
alteryx/featuretools#747 (comment)

[dsherry]

@rwedge @gsheni what was the problem in alteryx/featuretools#747 (comment) ? I see Roy said:

Our linting-related dependencies were out of date, and this was causing some errors if users were trying run make lint using the latest versions of these packages (example).

That sounds like an environment management problem. Now that we have the dependency update bot, we know that our unit tests pass on the latest version of all our pip dependencies, right? So we'd just need to keep our local development pip versions up to date, just like for any other package we develop against.

[gsheni]

@dsherry The problem was that the linter (make lint-fix) was reordering the import statements in __init__.py. This would cause the following error to be raised when make lint was ran:

ERROR: /work/featuretools/featuretools/init.py Imports are incorrectly sorted.