[tui] Make response to yes/no dialog case-insensitive

tui/simpletui.py

@@ -78,7 +78,7 @@ class SimpleTUI:
             SimpleTUI.info("(Yes/No)")
 
         while(True):
-            _user_input = input("> ")
+            _user_input = input("> ").lower()
             if _user_input.isalpha():
                 if _user_input in yes:
                     return True