DeprecationWarning for call to pkg_resources.declare_namespace() on import.

[adamchainz]

setuptools 67.3.0 has deprecated pkg_resources.declare_namespace(): https://setuptools.pypa.io/en/latest/history.html#v67-3-0

This is being triggered by importing intuit-oauth:

DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('intuitlib')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
    declare_namespace(pkg)

To remain a namespace package, the __init__.py may be deleted. But I'm not sure the package needs to be a namespace package, and we may be able to use an empty __init__.py instead.

[adamchainz]

namespace was added in e1483dc but without any explanation