Alert user when trying to make an invalid pickup

[dliberat]

If the user attempts to pick up a combination of cards that is invalid, they should receive some sort of visual feedback to alert them.

The following method in game_frame.py checks the validity of the pickup:

    def play_hand(self, hand_card):
        """Callback function executed when
        player clicks the "Play Hand" button.
        """
        if self.ronda.current_player is self.player:
            print(f"Attempting to play {hand_card} and\
                pick up: {self.selected_table_cards}")

            if is_valid_pickup(hand_card, self.selected_table_cards):
                self.ronda = self.ronda.play_turn(hand_card,
                                                  self.selected_table_cards)
                self.draw()
                self.play_next_move()
        else:
            print("not your turn")

Specifically, we can see that the if is_valid_pickup line does not have an else statement associated with it.

As for a specific implementation, at the moment I'm thinking that flashing something like this might be a good idea, but if someone wants to tackle this issue and has some other visual implementation in mind, it would be more than welcome.