Use relative imports in generated Python packages

[twosigmajab]

Please see swagger-api/swagger-codegen#8738

[twosigmajab]

I think the fix for this issue is small and simple. Is there interest in fixing it?

[wing328]

Please file a PR so that we can review the fix more easily.

[twosigmajab]

Not sure if/when I'll have a chance to do this. If someone wants to beat me to it, here is an example from when Connexion (the library you're using for Python server support) made this same improvement over 3 years ago:
spec-first/connexion@b77a5c7

So for example, instead of doing from {{packageName}} import util in places like this, you'd do something like from .util import ....