Django prompts to create new migrations when none are needed when a class is used in a field declaration

[Dan Loewenherz]

Create a model like so:

from django.db import models
from django.utils.deconstruct import deconstructible

@deconstructible
class IgnoreFormatString(object):
    def __init__(self, s):
        self.s = s

    def __str__(self):
        return self.s

    def __mod__(self, k):
        return self

class Product(models.Model):
    name = models.CharField(max_length=32, blank=True, null=True, error_messages={'invalid': IgnoreFormatString('Err, this is invalid.')})

Create a migration, and then run it. If you run "./manage.py migrate" once again, you'll get prompted with

  Your models have changes that are not yet reflected in a migration, and so won't be applied.
  Run 'manage.py makemigrations' to make new migrations, and then re-run 'manage.py migrate' to apply them.

Running makemigrations will create another migration, yet this message will continue to appear if the migration has already been applied.

[Dan Loewenherz]

Example project available at: ​https://github.com/dlo/django-migration-bug-23473

Thanks!