Relative imports in Python packages do not work

[lpsinger]

Describe the issue
According to https://arc.codes/docs/en/guides/developer-experience/dependency-management#relative-modules-%26-code-sharing-1, one can import relative modules in Lambdas (as in import .foo). First of all, the sample code in the documentation is not valid Python syntax:

>>> import .foo
  File "<stdin>", line 1
    import .foo
           ^
SyntaxError: invalid syntax

But secondly, the correct syntax, from . import foo, does not work in an Architect-managed Lambda. It fails with the following error message:

ImportError: attempted relative import with no known parent package

Steps to reproduce

1. Clone https://github.com/nasa-gcn/arc-python-example.
2. Run npm install.
3. Run npm start.
4. Open a browser and navigate to http://localhost:3333/.

Expected behavior
Browser should display JSON response: {"hello": "world"}

Screenshots

Desktop
Please complete the following information (if appropriate):

• OS: macOS
• Browser Safari

[lpsinger]

Note that absolute imports of modules that are defined locally within the Lambda don't work either. See nasa-gcn/gcn.nasa.gov#1678.