Update django-test-plus to 1.2.1

[pyup-bot]

This PR updates django-test-plus from 1.1.1 to 1.2.1.

Changelog

1.2.0

- Add optional `msg` argument to assertEqual method. Thanks davitovmasyan.

Links

• PyPI: https://pypi.org/project/django-test-plus
• Changelog: https://pyup.io/changelogs/django-test-plus/
• Repo: https://github.com/revsys/django-test-plus/

[coveralls]

Pull Request Test Coverage Report for Build 961

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 73.896%

---

Totals
Change from base Build 877:	0.0%
Covered Lines:	1840
Relevant Lines:	2490

---

💛 - Coveralls

[pyup-bot]

Closing this in favor of #248