Fix Flake8

[hugovk]

Fixes #401.

Includes #427, the first two commits. The others are new to this PR.

Flake8 found one bug: e3b445c

And one bit of old Python 2 code: 77c5488

Locally:

# Install
pip install -U flake8

# Run
flake8

Also run as part of:

pre-commit run --all-files

# Or
pre-commit run --all-files flake8

# Or
tox -e lint

Also run as part of the CI lint jobs.

[claudep]

Would be great to have a separate PR for this, with a test to complete coverage of that line.

[hugovk]

I think we could probably remove this whole if block. I don't see how column_widths can be None.

The default value is None in the method definition:

    def export_set_as_simple_table(cls, dataset, column_widths=None):

But it's only called from one place in export_set, and it includes a variable for column_widths, so it won't default to None:

        if use_simple_table and not force_grid:
            return cls.export_set_as_simple_table(dataset, column_widths)
        else:
            return cls.export_set_as_grid_table(dataset, column_widths)

Earlier in that method, it is set as:

        column_widths = cls._get_column_widths(dataset, max_table_width)

Which will always return a list:

        column_widths = [max(w, l) for w, l in zip(column_widths, word_lens)]
        return column_widths

A similar thing happens for the similar if block in export_set_as_grid_table.

These are all in _rst.py, the underscore denoting a private, internal code, and not part of the API.

What do you think?

[claudep]

Not sure, as the method itself is not prefixed with underscore, so if someone could very well call something like fmt = registry.get_format('rst'); fmt.export_set_as_simple_table(dataset) without breaking private rules. No strong opinion, but I would tend to fix and test.

[hugovk]

There we go! #433

[hugovk]

Let's not worry about Black for now, it's not essential.