Got it to end if the enter (return) key is used.

mine.py

@@ -8,7 +8,8 @@ class Mine:
     def __init__(self, position):
         self.position = position
 
-    def play_turn(self, game):
+    def handle_keystroke(self, keystroke, game):
+        if keystroke.name in ("KEY_ENTER"):
             if not game.is_empty(self.position):
                 game.log("You hit a mine at " + str(self.position) + ".")
                 game.end()