fix: Support relative imports for submodules

[di]

This PR adds support for importing from submodules relative to the directory where the function is defined.

[matthewrobertson]

LGTM

[jterblanche]

Supporting relative imports in functions framework is pointless if the live Cloud Functions environment doesn't support it as well.

[di]

Hi @jterblanche, I'm not sure what you mean, what do you think is missing here?

[jterblanche]

Nothing wrong here per se - but (unless I'm missing something) with target functions being invoked by Uvicorn on the Cloud Functions live platform in my opinion negates the need for this as relative imports can't be used there anyway.

[di]

@jterblanche The HTTP server being used (gunicorn vs flask's HTTP server) should have no effect on this feature.

To be extra clear here, since it seems like this is the source of the confusion: the Functions Framework (this repo) is used both for local development and is what is used to serve live Cloud Functions. Once this change is merged, released, and the Cloud Functions environment updated to include the new version of the framework, you'll be able to do relative imports in the Cloud Functions environment as well.

[di]

Also, @grant @matthewrobertson @KaylaNguyen FYI, I'm not a maintainer of this repo anymore, you'll need to merge/release this and my other PRs.

[jterblanche]

and is what is used to serve live Cloud Functions.

This is the bit I was missing thanks.