Upgrade pylint

[scop]

Description:

Upgrade pylint to 2.4.2 and astroid to 2.3.1, address raised issues.

https://pylint.readthedocs.io/en/latest/whatsnew/2.4.html
https://pylint.readthedocs.io/en/latest/whatsnew/changelog.html#what-s-new-in-pylint-2-4-1
https://pylint.readthedocs.io/en/latest/whatsnew/changelog.html#what-s-new-in-pylint-2-4-2

Bunch of false positive/bug workarounds needed, but some useful new issues caught too.

import-outside-toplevel disabled altogether for now, but I assume it would be ok to change those as well nowadays?

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[balloob]

Looks great!

Imports inside functions is indeed no longer necessary, so could be resolved (but would be a lot of work).

[frenck]

It would be great if we could resolve the imports since it would make an excellent guard.

Hacktoberfest issue?

[frenck]

I have created #27284 as a tracking issue. If you guys agree, I will mark it for Hacktoberfest & Help wanted.

[balloob]

That's fine. However, could we automate it ? Let me hack at it for 15m.

[balloob]

26 minutes. Not bad: #27288