Fix MySQL/Postgres compatibility with Django 1.10.
Review Request #9556 — Created Jan. 30, 2018 and submitted — Latest diff uploaded
Our constraint addition code for Django 1.10 wasn't providing the
"deferrable" variable to a template, which broke compatibility with both
MySQL and Postgres. This change adds the missing variable, allowing all
tests to run on MySQL and Postgres.
Ran unit tests on Django 1.6 through 1.10 using sqlite, MySQL, and
Postgres.