CI: Address linting errors in flake8 >= 3.8.1
xref #34150

This partially addresses the above issue by:

- Ignoring E741
- Fixing other linting errors

The issue with flake8-rst is handled temporarily in #34151, and the build here will fail the flake8-rst part until that is merged in.
great, does this complete the flake issues? e.g. can we unpin after this one? > great, does this complete the flake issues? e.g. can we unpin after this one?

It fixes all the issues with flake8 in the code, but it unfortunately doesn't fix the issue with flake8-rst kataev/flake8-rst#22.  That's a problem with the `flake8-rst` tool itself.

So, no, until `flake-rst` is fixed, we can't unpin. ok thanks. @MeeseeksDev backport to 1.0.x
 Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
$ git checkout 1.0.x
$ git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
$ git cherry-pick -m1 f9809fe9f206c96bda1e4be09ae17689fcd13adf
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
$ git commit -am 'Backport PR #34152: CI: Address linting errors in flake8 >= 3.8.1'
```

4. Push to a named branch :

```
git push YOURFORK 1.0.x:auto-backport-of-pr-34152-on-1.0.x
```

5. Create a PR against branch 1.0.x, I would have named this PR:

> "Backport PR #34152 on branch 1.0.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                 @jorisvandenbossche will start backporting this or could pin flake8 on 1.0.x? lmk > @jorisvandenbossche will start backporting this or could pin flake8 on 1.0.x? lmk

I would personally not care about backporting style related issues. Just pinning flake8 seems easier (or letting the lint build fail ..) > > @jorisvandenbossche will start backporting this or could pin flake8 on 1.0.x? lmk
> 
> I would personally not care about backporting style related issues. Just pinning flake8 seems easier (or letting the lint build fail ..)

yep. not backporting this at this time.