py3: compare response of crecord's confirmationwindow with str

confirmationwindow() returns a native string, as a result of calling
chr() on getch(). On Python 3, response.lower().startswith(b"y") leads
to a TypeError.

This fixes a crash when typing "r" in the curses interface of
interactive commit.

mercurial/crecord.py

@@ -1741,8 +1741,8 are you sure you want to review/edit and
         with self.ui.timeblockedsection(b'crecord'):
             response = self.confirmationwindow(confirmtext)
         if response is None:
-            response = b"n"
-        if response.lower().startswith(b"y"):
+            response = "n"
+        if response.lower().startswith("y"):
             return True
         else:
             return False