Add eslint rules and fix errors

[bansalnitish]

This PR Fixes #2909.

I have tested for all the rules mentioned in the issue. I have set the rules to error level when there are no false positives otherwise it is set to warning level.

There were 106 errors and warnings. Now we have 0 errors and 31 warnings. All these warnings are false positives.

I would also like to suggest to enforce the following rules:

• indent (especially this)
• semi
• space-unary-ops
• space-before-function-paren
• no-unused-vars

[davidfischer]

I changed the title to note that this is ESLint as opposed to PyLint.

[davidfischer]

Firstly, thank you for the first time contribution. ✨

This looks well thought through and well done and I'm happy to see this make it into master and get run on every commit! I was able to run tox -e eslint without issue and I see the same warnings and no errors. I think the changes to the .eslintrc are reasonable.

I do think your suggestions (especially indent) are good ideas. However, there's probably a lot of fixes around those. I don't think those other fixes should go in this PR.

[bansalnitish]

Firstly, thank you for the first time contribution.
This looks well thought through and well done and I'm happy to see this make it into master and get run on every commit!

Thank you @davidfischer!

However, there's probably a lot of fixes around those. I don't think those other fixes should go in this PR.

Shall I make a separate PR for that?

[bansalnitish]

Hi @davidfischer, is there anything else I need to do here?

[RichardLitt]

I believe this is just waiting for @ericholscher to merge. :)

[ericholscher]

I'll let @davidfischer do the honors!

[davidfischer]

I'll plan to merge this in the next hour or so today.

@bansalnitish, sure a separate PR would be great.

[bansalnitish]

Sure @davidfischer, I will make a separate PR!

[davidfischer]

For indentation, I ideally let's stick to 4 spaces similar to Python. https://eslint.org/docs/rules/indent