PEP 302 source loaders already decode appropriately

django/views/debug.py

@@ -354,6 +354,10 @@ class ExceptionReporter(object):
         if source is None:
             return None, [], None, []
 
+        # If we just read the source from a file, or if the loader did not
+        # apply tokenize.detect_encoding to decode the source into a Unicode
+        # string, then we should do that ourselves.
+        if isinstance(source[0], six.binary_type):
             encoding = 'ascii'
             for line in source[:2]:
                 # File coding may be specified. Match pattern from PEP-263