Given an object, return a boolean indicating whether it is an instance
    or subclass of :py:class:`Exception`.

def isexception(obj):
    """Given an object, return a boolean indicating whether it is an instance
    or subclass of :py:class:`Exception`.
    """
    if isinstance(obj, Exception):
        return True
    if isclass(obj) and issubclass(obj, Exception):
        return True
    return False