update file headers with license information (SPDX)
diff --git a/setup.py b/setup.py
index 17f4df0..fec5039 100644
--- a/setup.py
+++ b/setup.py
@@ -8,6 +8,10 @@
 #
 # For Python 3.x use the corresponding Python executable,
 # e.g. "python3 setup.py ..."
+#
+# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
+#
+# SPDX-License-Identifier:    BSD-3-Clause
 
 try:
     from setuptools import setup