How to make fun of throwing an exception in python?

I have a code like this:

def extract(data):
    if len(data) == 3:
       a = 3
    else:
        component = data.split("-")
        if len(component) == 3:
            a,b,c = component
        else:
            raise globals.myException("data1", "Incorrect format", data)

    return a,b,c

      

        
        
        
      

    

It's simplistic. I want to mock the globals.myException exception class. I'm doing it:

def test_extract_data_throws_exception(self):
        with patch('globals.myException') as mock: 
            mock.__init__("data1", "Incorrect format", "")
            with self.assertRaises(myException):
                self.assertEqual(extract(""), (""))

      

        
        
        
      

    

And I always get the error: "TypeError: Exceptions must be old style classes or derived from BaseException, not MagicMock"

EDIT . As @Aaron Digulla points out, fixing the monkeys is the right solution. I am posting a solution to help others.

def test_extract_data_throws_exception(self):
        #monkey patching
        class ReplaceClass(myException):
            def __init__(self, module, message, detail = u''):
                pass

        globals.myException = ReplaceClass
        with self.assertRaises(myException:
            self.assertEqual(extract(""), (""))