fix pylint errors

backend/src/products/exceptions.py

@@ -2,13 +2,16 @@ class ProductServiceError(Exception):
     def __init__(self, message: str):
         super().__init__(message)
 
+
 class ProductorNotFoundError(ProductServiceError):
     pass
 
+
 class ProductNotFoundError(ProductServiceError):
     pass
 
+
 class ProductCreateError(ProductServiceError):
     def __init__(self, message: str, field: str | None = None):
         super().__init__(message)
-        self.field = field
+        self.field = field