Handle relative imports in a package's __main__.py

I have a runnable package with __main__.py:

foo/
    __init__.py
    __main__.py

I can execute this package by running python -m foo. However you cannot directly create a PyInstaller application from this package:

• If you try pyinstaller -F foo, you'll get IOError: [Errno 21] Is a directory.
• If you try pyinstaller -F foo/__main__.py it will build, but then you'll get ValueError: Attempted relative import in non-package when you try to run it, presumably because it took __main__.py out of the context of its package.

The work around is to create a small "stub" application that lives outside of the package and calls into it:

from foo import main
main()

...and then point PyInstaller at the stub.

It seems that PyInstaller should be able to create an application by being pointed at the package directory.

I'm sorry if this has already been addressed, but I've been unable to find anything in the documentation or anywhere else:

• How can I convert a package to an exe using pyinstaller? (StackOverflow)

Start by reproducing the three cases in the issue: python -m foo, pyinstaller -F foo, and pyinstaller -F foo/__main__.py, using the shown package layout. Then trace PyInstaller's package entry-point handling. Done means a package directory can produce a runnable application while preserving relative imports, without requiring an external stub.