Update twine to 1.12.1

[pyup-bot]

This PR updates twine from 1.11.0 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

Links

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