Add google-endpoints to third_party/.

third_party/google-endpoints/tkinter/messagebox.py

Index: third_party/google-endpoints/tkinter/messagebox.py
diff --git a/third_party/google-endpoints/tkinter/messagebox.py b/third_party/google-endpoints/tkinter/messagebox.py
new file mode 100644
index 0000000000000000000000000000000000000000..3ed52e1fecfb3b787a86236c54bbecc195a15dc3
--- /dev/null
+++ b/third_party/google-endpoints/tkinter/messagebox.py
@@ -0,0 +1,13 @@
+from __future__ import absolute_import
+
+from future.utils import PY3
+
+if PY3:
+    from tkinter.messagebox import *
+else:
+    try:
+        from tkMessageBox import *
+    except ImportError:
+        raise ImportError('The tkMessageBox module is missing. Does your Py2 '
+                          'installation include tkinter?')
+