Revert "LocalizedUniqueSlugField refactored"

This reverts commit 03df76d6d7.

localized_fields/mixins.py

@@ -1,17 +1,38 @@
-from django.core.checks import Warning
+from django.db import transaction
+from django.conf import settings
+from django.db.utils import IntegrityError
+
 
 class AtomicSlugRetryMixin:
-    """A Mixin keeped for backwards compatibility"""
+    """Makes :see:LocalizedUniqueSlugField work by retrying upon
+    violation of the UNIQUE constraint."""
 
-    @classmethod
-    def check(cls, **kwargs):
-        errors = super().check(**kwargs)
-        errors.append(
-            Warning(
-                'localized_fields.AtomicSlugRetryMixin is deprecated',
-                hint='There is no need to use '
-                     'localized_fields.AtomicSlugRetryMixin',
-                obj=cls
-            )
+    def save(self, *args, **kwargs):
+        """Saves this model instance to the database."""
+
+        max_retries = getattr(
+            settings,
+            'LOCALIZED_FIELDS_MAX_RETRIES',
+            100
         )
-        return errors
+
+        if not hasattr(self, 'retries'):
+            self.retries = 0
+
+        with transaction.atomic():
+            try:
+                return super().save(*args, **kwargs)
+            except IntegrityError as ex:
+                # this is as retarded as it looks, there's no
+                # way we can put the retry logic inside the slug
+                # field class... we can also not only catch exceptions
+                # that apply to slug fields... so yea.. this is as
+                # retarded as it gets... i am sorry :(
+                if 'slug' not in str(ex):
+                    raise ex
+
+                if self.retries >= max_retries:
+                    raise ex
+
+        self.retries += 1
+        return self.save()