This makes the default behavior (without specifying `globalns` manually) more
predictable for users, finds the right globalns automatically.
Implementation for classes assumes has a `__module__` attribute and that module
is present in `sys.modules`. It does this recursively for all bases in the
MRO. For modules, the implementation just uses their `__dict__` directly.
This is backwards compatible, will just raise fewer exceptions in naive user
code.
Originally implemented and reviewed at https://github.com/python/typing/pull/470.
Łukasz Langa
Ivan Levkivskyi