pytype doesn't support aliasing an import from a class in pyi files (seen in pynamodb.models stub)

[rchen152]

pytype doesn't support the following:

from .exceptions import DoesNotExist as DoesNotExist
class Model(metaclass=MetaModel):
    DoesNotExist = DoesNotExist

seen in third_party/2and3/pynamodb/models.pyi.
This is because pytype only allows aliases to point to attributes on the same class. We can either fix this in our parser or change the alias to a constant (DoesNotExist: Type[DoesNotExist]), although that decreases readability and might confuse other type checkers.

[rchen152]

This seems to be fixed now!