Specify UTF-8 encoding for saving notebook as script.

IPython/frontend/html/notebook/notebookmanager.py

@@ -213,7 +213,7 b' class NotebookManager(LoggingConfigurable):'
         if self.save_script:
             pypath = os.path.splitext(path)[0] + '.py'
             try:
-                with io.open(pypath,'w') as f:
+                with io.open(pypath,'w', encoding='utf-8') as f:
                     current.write(nb, f, u'py')
             except Exception as e:
                 raise web.HTTPError(400, u'Unexpected error while saving notebook as script: %s' % e)