Fix TypeError when Python 3.x

Author: psmiraglia

tools/make_metadata.py

@@ -81,5 +81,5 @@
             xmldoc = None
 
         valid_instance(eid)
-        xmldoc = metadata_tostring_fix(eid, nspair, xmldoc)
+        xmldoc = metadata_tostring_fix(eid, nspair, xmldoc.encode())
         print(xmldoc.decode("utf-8"))