fix TypeError; use force_text to ensure that lazy instances are resolved to strings

Author: philall

rest_framework_xml/renderers.py

@@ -6,7 +6,7 @@
 from django.utils import six
 from django.utils.xmlutils import SimplerXMLGenerator
 from django.utils.six.moves import StringIO
-from django.utils.encoding import smart_text
+from django.utils.encoding import force_text
 from rest_framework.renderers import BaseRenderer
 
 
@@ -58,4 +58,4 @@ def _to_xml(self, xml, data):
             pass
 
         else:
-            xml.characters(smart_text(data))
+            xml.characters(force_text(data))