Support Python 3.7 about sanic-swagger

[hairychris]

This is the PEP that gets rid of GenericMeta: https://www.python.org/dev/peps/pep-0560/

[hairychris]

These "fixes" pass all the tests but I really don't think it's correct. Would you mind taking a look when you get the chance? https://github.com/hairychris/sanic-swagger/tree/patch-2

[abatilo]

I would agree that it doesn't feel like the correct approach, but in full transparency, I'm not really sure :/

I'm not sure that I understand what happened with GenericMeta when we moved to Python 3.7

[c-goosen]

I am also looking at this. We can add a dependency to keep GenericMeta? https://pypi.org/project/typing/

We can just create a class for GenericMeta?

First of all the fix @hairychris you could import GenericMeta as generic.

from typing import Generic as GenericMeta