spulec
Move type annotations inline and complete them
Now that the project is Python 3.6+, it can safely use inline type annotations. Doing so helps ensure that the types remain accurate and useful both internally and both projects that consume freezegun. For example, the pip project currently ignores missing freezegun types:
https://github.com/pypa/pip/blob/135faabfd62f8c3566fd4f99a5688316302cf1c8/tests/unit/test_self_check_outdated.py#L7
The CI system runs mypy on all support Python platforms as the stdlib API can change between releases. The code has been altered to use PEP-484 compliant version and platform checking as outlined at: https://www.python.org/dev/peps/pep-0484/#version-and-platform-checking
The type checker already found a couple of mistakes with internal API usage. This should help catch bugs in new pull requests earlier during CI.
The py.typed file is now installed alongside the package to be compliant with PEP-561: https://www.python.org/dev/peps/pep-0561/#packaging-type-information
Using the spec "type: ignore" comment and cast calls were only done as a last resort when the type checker couldn't be satisfied using more conventional approaches.
By switching to using the setuptools explicit package_data approach, the MANIFEST.in file was simplified.
I think it would be beneficial to land #418 and #416 first to make testing and review a bit nicer.