Django 2.0 had a bug when generating SQL for creating a unique index

where the name wasn't being quoted. This could result in statements with

syntax errors, and impacted some unit tests.
This change adds a runtime compatibility patch that overrides Django

2.0's _create_unique_sql() that adds quoting, if code is detected that

would skip the quoting.
This won't impact any version of Django that has the correct quoting

behavior.

Unit tests pass on Django 2.0.