added assertion and comment

git-svn-id: http://svn.code.sf.net/p/docutils/code/trunk/docutils@3653 929543f6-e4f2-0310-98a6-ba3bd3dd1d04

1 files changed, 5 insertions, 2 deletions

diff --git a/docutils/io.py b/docutils/io.py
index cfd24496c..91b70377e 100644
--- a/docutils/io.py
+++ b/docutils/io.py
@@ -148,8 +148,11 @@ class Output(TransformSpec):
         raise NotImplementedError
 
     def encode(self, data):
-        if ( self.encoding and self.encoding.lower() == 'unicode'
-             or not isinstance(data, UnicodeType)):
+        if self.encoding and self.encoding.lower() == 'unicode':
+            assert isinstance(data, UnicodeType), 'no unicode output'
+            return data
+        if not isinstance(data, UnicodeType):
+            # Non-unicode (e.g. binary) output.
             return data
         else:
             try: