Given that linters like pylint can already detect the common case of this issue when using `is` and `is not` to compare to a literal where == or != seems more appropriate, I don't think a warning is very useful.

In my experience people are more likely to run code through a linter than they are to ever run an interpreter with DeprecationWarning enabled.

I do like the concept of using a not visible by default warning, but I don't think adding a LintWarning or misusing DeprecationWarning adds much value.

I suggest closing this issue as won't fix / not a bug.