LocaleMiddleware didn't handle the ValueError raised by
get_supported_language_variant() when language codes were
over 500 characters.
Regression in 9e9792228a.
This is the exact same issue as refs #30408 but for creating a model with a
constraint containing % escapes instead of column addition. All of these issues
stem from a lack of SQL and parameters separation from the BaseConstraint DDL
generating methods preventing them from being mixed with other parts of the
schema alteration logic that do make use of parametrization on some backends
(e.g. Postgres, MySQL for DEFAULT).
Prior to the addition of Field.db_default and GeneratedField in 5.0
parametrization of DDL was never exercised on model creation so this is
effectively a bug with db_default as the GeneratedField case was addressed by
refs #35336.
Thanks Julien Chaumont for the report and Mariusz Felisiak for the review.
