rectories (standard pip behavior) or
zip/egg files (less common) are supported. The Python API for
introspecting data in packages is too limited to support other
installation methods the way this loader requires.

There is limited support for :pep:`420` namespace packages. The
template directory is assumed to only be in one namespace
contributor. Zip files contributing to a namespace are not
supported.

.. versionchanged:: 3.0
    No longer uses ``setuptools`` as a dependency.

.. versionchanged:: 3.0
    Limited PEP 420 namespace package support.
