fix #115 correctly

import_export_celery/fields.py

@@ -3,25 +3,18 @@
 
 
 def lazy_initialize_storage_class():
-    # If the user has specified a custom storage backend, use it.
-    if settings.STORAGES.get("IMPORT_EXPORT_CELERY_STORAGE"):
-        try:
-            # From Django 4.2 and later
-            from django.core.files.storage import storages
-            from django.core.files.storage.handler import InvalidStorageError
-            try:
-                storage_class = storages['IMPORT_EXPORT_CELERY_STORAGE']
-            except InvalidStorageError:
-                from django.utils.module_loading import import_string
-                storage_class = settings.DEFAULT_FILE_STORAGE
-                storage_class = import_string(storage_class)()
-        except ImportError:
-            # Deprecated since Django 4.2, Removed in Django 5.1
-            from django.core.files.storage import get_storage_class
-            storage_class = get_storage_class(
-                settings.STORAGES.get("IMPORT_EXPORT_CELERY_STORAGE")["BACKEND"]
-            )()
-        return storage_class
+    try:
+        # From Django 4.2 and later
+        from django.core.files.storage import storages
+        storage_alias = getattr(settings, "IMPORT_EXPORT_CELERY_STORAGE_ALIAS", "default")
+        storage_class = storages[storage_alias]
+    except ImportError:
+        # Deprecated since Django 4.2, Removed in Django 5.1
+        from django.core.files.storage import get_storage_class
+        old_storage = getattr(settings, "IMPORT_EXPORT_CELERY_STORAGE", settings.DEFAULT_FILE_STORAGE)
+        storage_class = get_storage_class(old_storage)()
+
+    return storage_class
 
 
 class ImportExportFileField(models.FileField):