Don't invoke reload(sys) and use StringIO objects instead of real files to capture stdin and stdout when needed (ensures all sys attributes remain unmodified after test_xmlrpc runs)

Lib/test/test_support.py

@@ -659,6 +659,9 @@ def captured_output(stream_name):
 def captured_stdout():
     return captured_output("stdout")
 
+def captured_stdin():
+    return captured_output("stdin")
+
 def gc_collect():
     """Force as many objects as possible to be collected.