Switch Python 3 native namespace packages for plugins

[omry]

Python 3 namespace packages

The following changes are required from plugins to be compliant with Hydra 1.0:

Hydra 0.11 used pkg_resource style packages for plugins, because they are backward compatible with Python 2.7.
Now that Hydra no longer supports Python 2.7, we can move to native namespace packages.

Doing it is quiet simple, but it's important that all plugins are going doing it, otherwise they might interfere with other plugins.

Remove hydra_plugins/__init__.py:

Previously, plugins had an hydra_plugins/__init__.py file that looked like:

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved                                                                                                                   
# type: ignore                                                                                                                                                                           
__path__ = __import__("pkgutil").extend_path(__path__, __name__)  

Remove it.

Update your setup.py to properly package your plugin

Previously setup.py has something like:

packages=find_packages(exclude=["tests", "example"]),

Without hydra_plugins/__init__.py, setuptools find_packages() will fail to pick up your plugin package, change it to (and of course the import of find_packages to find_namespace_packages too)

packages=find_namespace_packages(include=["hydra_plugins.*"])

If you have any other packages you are including with, you can combine find_namespace_packages() with find_package():

packages=find_packages(include=["coolstuff.*"]) + find_namespace_packages(include=["hydra_plugins.*"])

[mannatsingh]

For users still wanting to use find_packages for their regular packages, the change would involve concatenating the results from both find_packages and find_namespace_packages.

packages=find_packages(exclude=["tests", "example"]),

becomes

packages=find_packages(exclude=["tests", "example"]) + find_namespace_packages(include=["hydra_plugins.*"]),

[omry]

Thanks @mannatsingh, I updated the issue description to cover this.