I think it is better to left this on third-party linters.

* It is easy to catch patterns like `sys.version_info[0] == 3` or `sys.version[:3]` in the linter than in the Python compiler or interpreter. Linters are designed for this.

* Not always slicing sys.version is an error. For example, `sys.version[:sys.version.index(' ')]` is a valid code. Linters have options which allow to ignore some kind of warnings or warnings at the particular line.

* Users that ignore linters usually do not check the version. They wrote their scripts for the default system Python and update them when they become broken after system upgrade.