Rotating an image using pygame

Question

I'm trying to rotate an image using pygame. Here is my code thus far:

def main(self):
            self.size = width, height = 500, 500
            self.black = 0,0,0
            self.screen = pygame.display.set_mode(self.size)
            self.ball = pygame.image.load("deathstar.png")
            self.ballrect = self.ball.get_rect()
            self.ballcenter = self.ballrect.center

            while 1:
                    for event in pygame.event.get():
                            if event.type == pygame.QUIT:
                                    sys.exit()
                            elif event.type == pygame.MOUSEMOTION:
                                    print ("mouse at ", event.pos)
                                    self.rotate_image(some angle)
                    self.screen.fill(self.black)
                    self.screen.blit(self.ball, self.ballrect)
                    pygame.display.flip()

    def rotate_image(self, angle): 

How would I define rotate_image? I need it to rotate based on where the mouse is placed on the screen. Thanks!