Fixed #27924 -- Added support for cx_Oracle 5.3.

- Fixed Oracle backend due to cx_Oracle 5.3 change in the
Cursor.description behavior i.e. "Use None instead of 0 for items in
the Cursor.description attribute that do not have any validity.".
- Used cx_Oracle.Object.size() instead of len().
Thanks Tim Graham for the review.

docs/releases/1.11.txt

@@ -263,6 +263,8 @@ Database backends
   <mysql-isolation-level>`. To avoid possible data loss, it's recommended to
   switch from MySQL's default level, repeatable read, to read committed.
 
+* Added support for ``cx_Oracle`` 5.3.
+
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