handle encoding properly when outputting diff

morituri/test/common.py

@@ -26,11 +26,13 @@ def _diff(old, new, desc):
 
     raise AssertionError(
         ("\nError while comparing strings:\n"
-         "%s") % (output, ))
+         "%s") % (output.encode('utf-8'), ))
 
 
 def diffStrings(orig, new, desc='input'):
 
+    assert type(orig) == type(new)
+
     def _tolines(s):
         return [line + '\n' for line in s.split('\n')]