Support for Python versions <3.7?

[njsmith]

Not sure if this would violate your principles or not, but this hack would let you make this work on all versions of Python, I think :-)

[brettcannon]

As of right now I don't want the headache of caring about anything older than Python 3.7, but maybe I can be convinced. 😉

I could also make everything that is lazy simply not be lazy in the face of being older than Python 3.7 so that it can be a drop-in thing that's great in >=3.7 but a no-op in <3.7.

[brettcannon]

Thinking about this some more, making lazy_import() not lazy on <3.7 might be okay if a big project came forward and said they would totally use this if that was added. Everything else I have planned, though, just currently isn't structured to work in a pre-3.7 world. 😁