Update towncrier to 21.3.0

[pyup-bot]

This PR updates towncrier from 19.2.0 to 21.3.0.

Changelog

19.9.0

=============================

No significant changes.

19.9.0rc1

================================

Features
--------

- Add ``create`` subcommand, which can be used to quickly create a news
fragment command in the location defined by config. (`4 <https://github.com/hawkowl/towncrier/issues/4>`_)
- Add support for subcommands, meaning the functionality of the ``towncrier``
executable is now replaced by the ``build`` subcommand::

   $ towncrier build --draft

A new ``check`` subcommand is exposed. This is an alternative to calling the
``towncrier.check`` module manually::

   $ towncrier check

Calling ``towncrier`` without a subcommand will result in a call to the
``build`` subcommand to ensure backwards compatibility. This may be removed in a
future release. (`144 <https://github.com/hawkowl/towncrier/issues/144>`_)
- Towncrier's templating now allows configuration of the version header. *CUSTOM TEMPLATE USERS PLEASE NOTE: You will need to add the version header information to your template!* (`147 <https://github.com/hawkowl/towncrier/issues/147>`_)
- towncrier now accepts the --config argument to specify a custom configuration file (`157 <https://github.com/hawkowl/towncrier/issues/157>`_)
- There is now the option for ``all_bullets = false`` in the configuration.
Setting ``all_bullets`` to false means that news fragments have to include
the bullet point if they should be rendered as enumerations, otherwise
they are rendered directly (this means fragments can include a header.).
It is necessary to set this option to avoid (incorrect) automatic indentation
of multiline fragments that do not include bullet points.
The ``single-file-no-bullets.rst`` template gives an example of
using these options. (`158 <https://github.com/hawkowl/towncrier/issues/158>`_)
- The ``single_file`` option can now be added to the configuration file. When set to ``true``, the filename key can now be formattable with the ``name``, ``version``, and ``project_date`` format variables. This allows subsequent versions to be written out to new files instead of appended to an existing one. (`161 <https://github.com/hawkowl/towncrier/issues/161>`_)
- You can now specify Towncrier-bundled templates in your configuration file. Available templates are `default`, `hr-between-versions` (as used in attrs), and `single-file-no-bullets`. (`162 <https://github.com/hawkowl/towncrier/issues/162>`_)


Bugfixes
--------

- Accept newsfragment filenames with multiple dots, like `fix-1.2.3.bugfix`. (`142 <https://github.com/hawkowl/towncrier/issues/142>`_)


Deprecations and Removals
-------------------------

- The `--pyproject` option for `towncrier check` is now replaced with `--config`, for consistency with other commands. (`162 <https://github.com/hawkowl/towncrier/issues/162>`_)

Links

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

[pyup-bot]

Closing this in favor of #50