basestring normailization for python3.

secretary.py

@@ -14,7 +14,6 @@ Secretary
         engine = Renderer(template_file)
         result = engine.render(template_var1=...)
 """
-from __future__ import unicode_literals, print_function
 
 import io
 import re
@@ -23,6 +22,24 @@ import logging
 import zipfile
 from xml.dom.minidom import parseString
 from jinja2 import Environment, Undefined
+from __future__ import unicode_literals, print_function
+
+# Test python versions and normalize calls to basestring, unicode, etc.
+try:
+    unicode = unicode
+except NameError:
+    # 'unicode' is undefined, must be Python 3
+    str = str
+    unicode = str
+    bytes = bytes
+    basestring = (str,bytes)
+else:
+    # 'unicode' exists, must be Python 2
+    str = str
+    unicode = unicode
+    bytes = str
+    basestring = basestring
+
 
 FLOW_REFERENCES = {
     'text:p'             : 'text:p',