Old-style class defined
Used when a class is defined using the old style.
This message belongs to the newstyle checker.
In Python 2.x, old-style classes are defined by not inheriting from a base class or by inheriting from other old-style classes. New-style classes are defined by inheriting from class object or from other new-style classes.
Python 3.x supports only new-style classes; if no base class is specified on a class definition, the class implicitly inherits from object.
It is recommended to define only new-style classes, because they are properly integrated into Python's type system. See Python docs article: New-Style Classes for details.