Fix RST syntax.

shell/README.rst

@@ -40,13 +40,14 @@ Example session:
     
 Troubleshooting
 ===============
-If the command does nothing, or if you have the error
+
+If the command does nothing, or if you have the error::
 
     Usage: odoo.py [options]
 
     odoo.py: error: unrecognized parameters: 'shell'
 
-it is surely because of the order of the parameters. Try the following:
+it is surely because of the order of the parameters. Try the following::
 
     $ ./odoo.py --addons-path=<your_path1>,<your_path2> shell --config=<your_config_file> -d <dbname>