Drop # type: ignore comments in cli subpackage

[pradyunsg]

Follow up on #6727 (review)

[mathagician]

Hello @pradyunsg, I would like to work on this issue. Could you please assign this to me?

[pradyunsg]

@mathagician Sure! Go ahead! :)

Note that this issue will entail fixing the mypy issues, that are being silenced by the ignore comments.

[rohitsanj]

Hey @mathagician let me know if you are still working on this, I'd like to work on it as well 😄

@pradyunsg I'm not sure how I can reproduce the mypy issues in cli subpackage. I ran the command tox -e lint but it just showed some mypy errors in another file and failed with this error:

ERROR: InvocationError for command /Users/rohitsanjay/pip/.tox/lint/bin/pre-commit run --all-files --show-diff-on-failure (exited with code 1)

[pradyunsg]

@rohitsanj please post the entire output, otherwise it is not possible to get the required context to help answer your questions.

[deveshks]

Hi @pradyunsg

Can I take up this PR? Also what is the fix you are looking for the PR here? Is the aim to remove all #type: ignore comments and fix the lines of code where it was present one by one?

[pradyunsg]

Yea, basically. :)

[deveshks]

I was experimenting a bit, and found that if InterruptibleMixin
and WindowsMixin are defined as subclasses of pip._vendor.progress.Infinite and
DownloadProgressMixin as a subclass of [pip._vendor.progress.Progress]](https://github.com/pypa/pip/blob/master/src/pip/_vendor/progress/__init__.py#L136), most of the remaining type: ignore comments can be gotten rid of.

But I am not sure this is the correct way, and if it defeats the purpose of defining these classes as Mixin.