fix output from RawConfigParser.write and ConfigParser.write for None
values (http://bugs.python.org/issue7005)
(merged r84443 from the release27-mmaint branch, with changes to reflect
changes in Python 3)
diff --git a/Lib/configparser.py b/Lib/configparser.py
index eb29b02..fb39ac3 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -637,7 +637,7 @@
         for key, value in section_items:
             if key == "__name__":
                 continue
-            if value is not None:
+            if (value is not None) or (self._optcre == self.OPTCRE):
                 value = delimiter + str(value).replace('\n', '\n\t')
             else:
                 value = ""