Fixed flake8 warnings.
Fixed an instance of 'an' before a word beginning with a consonant.
Fixed #23452 -- Prevented infinite migrations for empty unique/index_together.

Thanks fwkroon for the report.
Fixed #23417 -- Completed locale formats for zh_CN, zh_Hans, zh_Hant and zh_TW.
Corrected grammar in migrations error message.
Fixed #20743 -- Added support for keyfile/certfile in SMTP connections.

Thanks jwmayfield, serg.partizan, and Wojciech Banaś for work on the patch.
Fixed typo in topics/forms/formsets.txt
Corrected indentation in a contrib.humanize test; refs #23340.

Thanks Zach Borboa for the report.
Avoided using deprecated version of importlib; refs #23418.
Added some items to the 1.7.1 release notes.
Added ordering to prevent non-deterministic test failure; refs #23099.