Yaraslau Zhylko

@chayim @dvora-h This one is ready for review. But I do not know what's the best way to fix the issue with `pypy-3.7`. Deprecate `pypy-3.7`? Find some replacement for `typed-ast`?...

@chayim Fixed the `${{ matrix.pyver }}` part (see review comment above). But what should we do with `mypy` and `types-ast` for `pypy-3.7`?

@chayim Now Dependency Audit fails as well. 😅 Will merging #483 fix that? All GitHub actions seem to be green for it.

@chayim Limited `mypy` to `cpython` implementation only to solve the `types-ast` issue. Please let me know if we should handle this differently.

PR with a fix: #479