Also check and restore identity of sys.path, sys.argv and os.environ rather than just their values (this picked up a few more misbehaving tests)

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)

Enhancement to the new environment checking code to print the changed items under -vv. Also includes a small tweak to allow underscores in the names of resources.

an obscure, undocumentated feature so no test was added. Closes
issue #1101399.