Fix and Apply CI Lint Checks

[mfleader]

Changes introduced with this PR

• Fix CI checks on style and linting.
• Apply required style formatting and linting (enforcing CI checks required this).
• black was removed as a style format checker. At this point, it is only used to converge the code base towards flake8 acceptance.

Almost no style checks nor linting was performed on this repository until now, so this is a big one.

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[jaredoconnell]

It looks good. I don't like all of the new format, but we agreed on black and flake8. I see some higher risk changes, like messing with isinstance. If those are well tested, or applied automatically, then it's fine. The CI is passing.

[dbutenhof]

I see some higher risk changes, like messing with isinstance.

That's an interesting point, and the answer really depends on the intent of the check.

type(a) is Foo is True only if a is actually a Foo() instance, exactly; whereas isinstance(a, Foo) is True if a is a Foo or a subclass of Foo.

I think in the context I read, the latter is more appropriate, in which case using type means that subclassing will break the tests whereas the new isinstance is resistant to that.

But of course if subclasses need not apply, then type is better... (I think that's rarely true or appropriate...)