Update importlib-metadata to 3.1.1

[pyup-bot]

This PR updates importlib-metadata from 1.7.0 to 3.1.1.

Changelog

3.1.1

======

3.1.0

======

* Merge with 2.1.0.

3.0.0

======

* Require Python 3.6 or later.

2.1.1

======

* 261: Restored compatibility for package discovery for
metadata without version in the name and for legacy
eggs.

2.1.0

======

* 253: When querying for package metadata, the lookup
now honors
`package normalization rules <https://packaging.python.org/specifications/recording-installed-packages/>`_.

2.0.0

======

* ``importlib_metadata`` no longer presents a
``__version__`` attribute. Consumers wishing to
resolve the version of the package should query it
directly with
``importlib_metadata.version('importlib-metadata')``.
Closes 71.

Links

• PyPI: https://pypi.org/project/importlib-metadata
• Changelog: https://pyup.io/changelogs/importlib-metadata/
• Repo: https://github.com/python/importlib_metadata

[pyup-bot]

Closing this in favor of #42