Always convert Text.index result to string.
This improves compatibility with Tcl 8.5, which would
otherwise return textindex objects.
diff --git a/Lib/lib-tk/Tkinter.py b/Lib/lib-tk/Tkinter.py
index f3f99f4..3ec3407 100644
--- a/Lib/lib-tk/Tkinter.py
+++ b/Lib/lib-tk/Tkinter.py
@@ -2981,7 +2981,7 @@
         return self.tk.call(self._w, "image", "names")
     def index(self, index):
         """Return the index in the form line.char for INDEX."""
-        return self.tk.call(self._w, 'index', index)
+        return str(self.tk.call(self._w, 'index', index))
     def insert(self, index, chars, *args):
         """Insert CHARS before the characters at INDEX. An additional
         tag can be given in ARGS. Additional CHARS and tags can follow in ARGS."""