Update webargs to 4.1.2

[pyup-bot]

This PR updates webargs from 4.1.1 to 4.1.2.

Changelog

4.1.2

******************

Bug fixes:

* Fix serialization behavior of ``DelimitedList`` (:pr:`319`).
Thanks :user:`lee3164` for the PR.

Other changes:

* Test against Python 3.7.

Links

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

[coveralls]

Coverage remained the same at 88.007% when pulling 3e5cee2 on pyup-update-webargs-4.1.1-to-4.1.2 into ad6935b on master.

[coveralls]

Coverage remained the same at 88.007% when pulling 3e5cee2 on pyup-update-webargs-4.1.1-to-4.1.2 into ad6935b on master.