Require specifying encoding when using "open" (re: PEP597)

[Sxderp]

Rule request

Inspired by https://www.python.org/dev/peps/pep-0597

The PEP is still draft, but I think WPS can implement before adoption. Even if the PEP is rejected I think this is a good idea.

Required specifying "encoding" to open. Even if it's just None.

Thesis

Not specifying the encoding could be considered a bug. Making the effort to choose which encoding is better. At the moment there is no builtin "locale" so we have to settle for None or call locale.getpreferredencoding() all the time. The second option is a bit clumbersome.

## Wrong
with open('filename.txt') as fd:
    fd.read()

## Correct
with open('filename.txt', encoding='ascii') as fd:
  fd.read()

with open('filename.txt', encoding='utf8') as fd:
  fd.read()

# Unfortunately we have to settle for "None" to indicate "locale".
with open('filename.txt', encoding=None) as fd:
  fd.read()

Reasoning

Everything described in the PEP.

[sobolevn]

Great idea, I will totally do this (either here or in typed-linter that I am developing right now)!

Why not just implementing it here? Because typed-linter will support auto-fixing problems. And this looks like it can be autofixed.

[GibranHL0]

I'd like to take this issue as well, pls 😌

[GibranHL0]

#2082 Opened

[lensvol]

Is this still opened?

[sobolevn]

There's a PR for it: #2082

I will merge it into 0.16.0 later this week.