Django throws error when different apps with different models have the same name table name.

[dev-c]

Error message:
table_name: (models.E028) db_table 'table_name' is used by multiple models: base.ModelName, app2.ModelName.

We have a Base app that points to a central database and that has its own tables. We then have multiple Apps that talk to their own databases. Some share the same table names.
We have used this setup for a while, but after upgrading to Django 2.2 we're getting an error saying we're not allowed 2 apps, with 2 different models to have the same table names.

Is this correct behavior? We've had to roll back to Django 2.0 for now.

[Claude Paroz]

Regression in [5d25804eaf81795c7d457e5a2a9f0b9b0989136c], ticket #20098.
My opinion is that as soon as the project has a non-empty DATABASE_ROUTERS setting, the error should be turned into a warning, as it becomes difficult to say for sure that it's an error. And then the project can add the warning in SILENCED_SYSTEM_CHECKS.

[Adnan Umer]

I agree with your opinion. Assigning to myself, patch on its way

Replying to Claude Paroz:

Regression in [5d25804eaf81795c7d457e5a2a9f0b9b0989136c], ticket #20098.
My opinion is that as soon as the project has a non-empty DATABASE_ROUTERS setting, the error should be turned into a warning, as it becomes difficult to say for sure that it's an error. And then the project can add the warning in SILENCED_SYSTEM_CHECKS.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 8d351907:

Fixed #30673 -- Relaxed system check for db_table collision when database routers are installed by turning the error into a warning.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 1265a26b:

[2.2.x] Fixed #30673 -- Relaxed system check for db_table collision when database routers are installed by turning the error into a warning.

Backport of 8d3519071ec001f763b70a3a1f98ae2e980bd552 from master.