Fix the minidom test.
In order to do this, I added an optional encoding argument to io.StringIO.
The toprettyxml() function returns bytes when you specify an encoding now.
diff --git a/Lib/io.py b/Lib/io.py
index 96226e4..9a4f956 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -1262,11 +1262,13 @@
 
     # XXX This is really slow, but fully functional
 
-    def __init__(self, initial_value=""):
-        super(StringIO, self).__init__(BytesIO(), "utf-8")
+    def __init__(self, initial_value="", encoding="utf-8", newline=None):
+        super(StringIO, self).__init__(BytesIO(),
+                                       encoding=encoding,
+                                       newline=newline)
         if initial_value:
             self.write(initial_value)
             self.seek(0)
 
     def getvalue(self):
-        return self.buffer.getvalue().decode("utf-8")
+        return self.buffer.getvalue().decode(self._encoding)