`from __future__ import annotations` is 3.7+

[nickdrozd]

Current problem

from __future__ import annotations doesn't work on Python versions 3.6 and earlier.

Desired solution

When running with py-version=3.6 or earlier, flag it.

Additional context

• https://docs.python.org/3/library/__future__.html#module-contents
• https://peps.python.org/pep-0563/