Update twine to 1.12.1

[pyup-bot]

This PR updates twine from 1.9.1 to 1.12.1.

Changelog

1.12.1

* :bug:`404` Fix regression with upload exit code

1.12.0

* :feature:`395 major` Add ``twine check`` command to check long description
* :feature:`392 major` Drop support for Python 3.3
* :feature:`363` Empower ``--skip-existing`` for Artifactory repositories
* :bug:`367` Avoid MD5 when Python is compiled in FIPS mode

1.11.0

* :bug:`269 major` Avoid uploading to PyPI when given alternate
repository URL, and require ``http://`` or ``https://`` in
``repository_url``.
* :support:`277` Add instructions on how to use keyring.
* :support:`314` Add new maintainer, release checklists.
* :bug:`322 major` Raise exception if attempting upload to deprecated legacy
PyPI URLs.
* :feature:`320` Remove PyPI as default ``register`` package index.
* :feature:`319` Support Metadata 2.1 (:pep:`566`), including Markdown
for ``description`` fields.
* :support:`318` `Update PyPI URLs
<https://packaging.python.org/guides/migrating-to-pypi-org/>`_.

1.10.0

* :bug:`315 major` Degrade gracefully when keyring is unavailable
* :feature:`304` Reorganize & improve user & developer documentation.
* :feature:`46` Link to changelog from ``README``
* :feature:`295` Add doc building instructions
* :feature:`296` Add architecture overview to docs
* :feature:`303` Revise docs predicting future of ``twine``
* :bug:`298 major` Fix syntax highlighting in ``README``
* :bug:`299 major` Fix changelog formatting
* :bug:`200 major` Remove obsolete registration guidance
* :bug:`286 major` Fix Travis CI and test configuration
* :feature:`257` Declare support for Python 3.6
* :bug:`297 major` Fix Read the Docs, tox, Travis configuration
* :bug:`268 major` Print progress to ``stdout``, not ``stderr``
* :bug:`265 major` Fix ``--repository[-url]`` help text
* :feature:`256` Improve progressbar

Links

• PyPI: https://pypi.org/project/twine
• Changelog: https://pyup.io/changelogs/twine/
• Docs: https://twine.readthedocs.io/

[pyup-bot]

Closing this in favor of #126