Add pre-upload.py sample
diff --git a/pre-upload.py b/pre-upload.py
new file mode 100644
index 0000000..2ff373f
--- /dev/null
+++ b/pre-upload.py
@@ -0,0 +1,11 @@
+def main(project_list, **kwargs):
+  print ('These projects will be uploaded: %s' %
+         ', '.join(project_list))
+  print ('I am being a good boy and ignoring anything in kwargs\n'
+         'that I don\'t understand.')
+  print 'I fail 50% of the time.  How flaky.'
+  if random.random() <= .5:
+    raise Exception('Pre-upload hook failed.  Have a nice day.')
+
+if __name__ == '__main__':                                                       
+  main()