fix type check

Author: bckohan

django_enum/fields.py

@@ -181,7 +181,8 @@ def to_python(self, value: Any) -> Union[Choices, Any]:
             return self._try_coerce(value)
         except ValueError as err:
             raise ValidationError(
-                f"'{value}' is not a valid {self.enum.__name__}."
+                f"'{value}' is not a valid "
+                f"{self.enum.__name__ if self.enum else ''}."
             ) from err
 
     def validate(self, value: Any, model_instance: Model):

django_enum/tests/examples/migrations/0001_initial.py

@@ -1,7 +1,7 @@
 # Generated by Django 3.2.14 on 2022-08-09 03:04
 
-from django.db import migrations, models
 import django_enum.fields
+from django.db import migrations, models
 
 
 class Migration(migrations.Migration):