Update keyring to 19.3.0

[pyup-bot]

This PR updates keyring from 19.2.0 to 19.3.0.

Changelog

19.3.0

------

* Switch to `importlib.metadata
<https://docs.python.org/3/library/importlib.metadata.html>`_
for loading entry points. Removes one dependency on Python 3.8.

* Added new ``KeyringBackend.set_properties_from_env``.

* 382: Add support for alternate persistence scopes for Windows
backend. Set ``.persist`` to "local machine" or "session"
to enable the alternate scopes or "enterprise" to use the
default scope.

* 404: Improve import times when a backend is specifically
configured by lazily calling ``get_all_keyring``.

Links

• PyPI: https://pypi.org/project/keyring
• Changelog: https://pyup.io/changelogs/keyring/
• Repo: https://github.com/jaraco/keyring