Checks performed during Permission creation should use the check framework.

[Simon Charette]

The django.contrib.auth.management.check_permission function that is connected to the post_migrate signal performs static model analysis checks that should rely on the check framework. At the moment a ValidationError or a CommandError is raised when a check fails.

The checks performed are the following:

1. Check that custom permissions don't clash with built-ins and are not duplicated;
2. Check that models verbose_name doesn't exceed a certain length based on the Permission.name.max_length;
3. Check that permissions name doesn't exceed a certain length based on the Permission.name.max_length.

For 2. and 3. I suggest we make them issue a check.Warning with a message noting that the name will be truncated to N characters instead of crashing with an IntegrityError if the check is ignored/disabled.

[Simon Charette]

​https://github.com/django/django/pull/6421

[Tim Graham]

Those checks were added before the permission name max_length was increased from 50 to 255 (#8162). Therefore I expect few if any users to exceed that limit these days. I don't see much benefit to adding truncation logic as proposed.

[Simon Charette]

Alright, I'll add them as errors later today in this case.

[Simon Charette]

Just ported the permission names max length checks as well.

[Simon Charette <charette.s@…>]

In a872194:

Fixed #26470 -- Converted auth permission validation to system checks.

Thanks Tim for the review.